ADHD - Diagnostic methods

Author: Ulrich Brennecke
Review: Dipl.-Psych. Waldemar Zdero

An ADHD diagnosis is traditionally determined using questionnaires, interviews and tests. In principle, several different instruments should be used. This means that several questionnaires, several tests and a personal interview by the diagnostician are essential for a good diagnosis.
The agreement between questionnaires and tests is limited despite the validity and reliability of the respective tests being checked.
Symptoms of ADHD also occur in other disorders. A study of 10 disorders found that 60% of the symptoms occurred in at least half of all disorders and were assessed in the respective disorder-specific questionnaires and tests.¹

ADHD is typically diagnosed by the number of relevant symptoms. This increases the diagnostic accuracy of ADHD.² This model was exemplified by Barkley:

• Non-affected people often have 1 to 2 of 18 symptoms on average (around 5%)³
• On average, people with ADHD often have 12 of these 18 symptoms (around 66%)³
  The online screening of the ADxS.org symptom test is based on this model. The test queries 45 symptoms, but is not medically validated and is not used for medical diagnosis.

Neuropsychological tests⁴ or individual biomarkers are too imprecise to diagnose ADHD. We suspect that, similar to the rating scales for symptoms of ADHD, which are based not only on a single symptom but on the cluster of symptoms common in ADHD, a test cluster of a group of neuropsychological tests or measurement of a group of biomarkers typical of ADHD could result in adequate test accuracy. Since ADHD is a syndrome, i.e. a multitude of different causes that manifest themselves in common symptoms, biomarkers should only be able to measure either the mechanisms that mediate the common symptoms (although here too, with the dopamine and noradrenaline systems alone, there are several similar, because functionally redundant, systems) or individual causes of the syndrome, but barely all of them. Against this background, it is surprising that the improvement of the detection rate through individual biomarkers continues to be pursued instead of researching the appropriate combination of different biomarkers that, in their entirety, enable ADHD diagnostics. There are individual approaches that pursue this idea.⁵⁶

• 1. Questionnaires for ADHD diagnosis
  • 1.1. Clinical expert scales
  • 1.2. Self-assessment questionnaires
• 2. Interviews / instruments for ADHD diagnostics
  • 2.1. Interviews / instruments with preschool children
  • 2.2. Interviews / instruments with schoolchildren / adolescents
  • 2.3. Interviews / instruments for adults
    • 2.3.1. Tests for ADHD symptoms in adulthood
    • 2.3.2. Tests for ADHD in childhood
  • 2.4. Live interviews compared to video testing
  • 2.5. Online self-tests
• 3. Tests for ADHD diagnostics
  • 3.1. Test procedure for ADHD diagnostics
    • 3.1.1. Neuropsychological test procedures
    • 3.1.2. Individual attention and reaction tests
      • 3.1.2.1. Stroop Test
      • 3.1.2.2. Stroop Plus Test
      • 3.1.2.3. Perceptual Selectivity Test
      • 3.1.2.4. N-back test
      • 3.1.2.5. Stop signal task (SST)
      • 3.1.2.6. Children’s Color Trail Test (1/2)
      • 3.1.2.7. Continuous Performance Test (CPT)
      • 3.1.2.8. Digit Span Test
      • 3.1.2.9. Wisconsin Card Sorting Test
      • 3.1.2.10. Qb test
    • 3.1.3. Test matches
    • 3.1.4. Virtual seminar room (VSR)
    • 3.1.5. AI test systems: major progress in the lab
  • 3.2. Problems with neuropsychological ADHD tests
    • 3.2.1. People with ADHD perform as well in tests as people without ADHD with the right motivation
      • 3.2.1.1. No / fewer ADHD symptoms in tests with high motivation
        • 3.2.1.1.1. Attention tests
        • 3.2.1.1.2. Impulsivity (inhibition) can be improved through rewards
        • 3.2.1.1.3. Reaction times: Reward accelerates reaction times and reduces reaction variance only in ADHD
      • 3.2.1.2. ADHD symptoms more visible in low-demand tests
    • 3.2.2. ADHD symptoms and relationship to test subject
    • 3.2.3. Smoking masks ADHD symptoms
    • 3.2.4. 116.200 Different ADHD “subtypes
    • 3.2.5. Evaluations by parents and teachers differ significantly
    • 3.2.6. Conclusions
• 4. Objective measurement methods (biomarkers) for ADHD
  • 4.1. EEG / QEEG measurement
    • 4.1.1. Beta-theta ratio as a diagnostic tool
    • 4.1.2. Changed slope / offset of the 1/f noise in the EEG
    • 4.1.3. Measurement of evoked potentials
    • 4.1.4. Measurement of rsEEG
    • 4.1.5. Measurement of non-linear EEG values
    • 4.1.6. Phase space reconstruction of the EEG
    • 4.1.7. Gamma levels reduced in ADHD
    • 4.1.8. EPSPatNet86: 8-point EEG measurement on 85 wavelets
    • 4.1.9. EEG analysis using VMD-HT
    • 4.1.10. Brain complexity
  • 4.2. Functional near-infrared spectroscopy (fNIRS)
  • 4.3. Genetic testing
  • 4.4. Endocrine and physical biomarkers
    • 4.4.1. Measurement of cortisol levels
      • 4.4.1.1. Measurement of the basal cortisol level
      • 4.4.1.2. Measurement of the phasic cortisol response to psychological stressors
    • 4.4.2. Dexamethasone/ACTH/CRH test?
    • 4.4.3. Mineral analysis
    • 4.4.4. Axonal damage to the white matter
    • 4.4.5. 24-Hour movement profiles
    • 4.4.6. Facial features
      • 4.4.6.1. Facial morphology in ADHD
      • 4.4.6.2. Facial morphology in ASD
    • 4.4.7. Analysis of MRI brain images
    • 4.4.8. Analysis of urine values (-)
    • 4.4.9. Analysis of eye values
      • 4.4.9.1. Electroretinography (ERG)
      • 4.4.9.2. Pupillometry
      • 4.4.9.3. Eye tracker: Duration of target fixation
• 5. Diagnostic guidelines
  • 5.1. Psychiatric anamnesis
  • 5.2. Differential diagnosis
    • 5.2.1. Exclusion of organic causes
    • 5.2.2. Exclusion of other psychological causes
  • 5.3. Interview with parents/confidants
  • 5.4. Primary school reports
  • 5.5. Standardized survey of ADHD symptoms
  • 5.6. Test psychological performance diagnostics

1. Questionnaires for ADHD diagnosis¶

Questionnaires are filled out by people with ADHD themselves and their caregivers (parents, teachers, friends).

Questionnaires are very subjective and involve the risk that the respondent’s personal opinion about ADHD itself influences the response scale. It can happen that parents reject the diagnosis of ADHD in principle, especially in their own child. Likewise, subjective ideas of people with ADHD (perhaps that they “want” a diagnosis in the hope of finding a solution to their suffering, perhaps that they reject a diagnosis because they fundamentally reject ADHD or to avoid stigmatization) or the change in assessment standards due to intensive prior employment can distort the results (bias).

For example, in tests of elimination diets for ADHD, the results of parent surveys are always far more positive than the results of objective tests.⁷ As this occurs even in double-blind studies, there is a considerable bias on the part of parents to report the subjectively desired result (that ADHD can be treated with a diet rather than with critically considered medication).
However, it is also conceivable that the parents were already enthusiastic about the small improvements that an elimination diet can bring or that a placebo effect can have on the child with ADHD and were not even aware of the much better effect that could be achieved through medication or therapy, or at least were not aware of it at the time of the assessment.

Suitable questionnaires for ADHD are:

1.1. Clinical expert scales¶

Clinical expert scales:⁸

• Diagnostic checklist (ADHD-DC)
• IDA-R (Integrated Diagnosis of ADHD, revised version)
• Wender-Reimherr Interview (WRI)
• Conners Scales of Attention and Behavior - External Assessment (CAARS-O) ⁹

• Conners 3-Parent Short Form, C 3-P(S)¹⁰
• Conners 3-Teacher Short Form, C 3-T(S)¹⁰
• Conners Early Childhood.¹¹
• Child Behavior Checklist, CBCL/1.5-5 (parent questionnaire on behavior)
  of preschool children between 1.5 and 5 years)¹²¹⁰
• Child Behavior Checklist, CBCL/6-18 (Parent Behavior Questionnaire)
  of children and young people from 4 to 18 years)¹³¹⁰
• Child and Adolescent Behavior Inventory (CABI)
  CABI is a parent questionnaire with 75 questions.
  CABI is more accurate than CBCL in relation to ADHD and anxiety, CBCL is more accurate in relation to conduct disorder (CD) and oppositional defiant disorder (ODD).¹⁴
• Teacher Rating Form (TFR 6-18)¹³¹⁰
• Parent/Teacher Questionaries (Conner)¹⁵
• Parent / teacher questionnaires¹⁶
• Quantitative Behavior Test (QbTest)
  70% accuracy in adults aged 55 to 79 years. In combination with self-reported ADHD symptom severity, 91% accuracy.¹⁷¹⁸
• Assessment form for parents, teachers and educators (FBB-HKS)¹⁹
• Before School Functioning Questionnaire (BSFQ)²⁰
• Parent Rating of Evening and Morning Behavior Scale, Revised (PREMB-R)²⁰
• ADHD/ODDEFB: ADHD/ODD parent questionnaire. Steinhausen (2002)
• AD-H-D Test System: Attention and Hyperactivity Deficit Disorder Questionnaire Test. Sponsel (2002)
• CAPT: Continuous Attention Performance Test - German version. Nubel, Starzacher, Grohmann (2006)
• BADD: Brown Attention Deficit Disorders Scale, a self-completion questionnaire with 40 items to assess cognitive ADHD symptoms
• Q-ADHD-Child: a rating scale for childhood ADHD symptoms according to DSM-IV and ICD-10 criteria²¹

1.2. Self-assessment questionnaires¶

Self-assessment questionnaires:⁸

• ADHD self-assessment scale (ADHD-SB)
• ADHD screening for adults (ADHD-E) (including severity of severity compared to standard values)
• Conners Scales of Attention and Behavior for Adults - Self-Assessment (CAARS-S)
• Cologne ADHD Test for Adults (KATE)
  • Folder with various tests and evaluation instructions
  • ASRS 1.1.
• Wender-Reimherr self-assessment (WR-SB)

• ASRS 1.1, ADHD screening of the WHO²²

  • 6-item short screening
  • 18-item long screening
  • The ASRS rating scales have a very limited diagnostic value²³
    A meta-study of 9 ADHD questionnaires found that only 37% asked identical symptoms/behaviors.¹ Most of the questionnaires for children were answered by parents, most of the questionnaires for adults were self-tests.

• Youth Self-Report, YSR/11-18 (questionnaire for young people)²⁴

• Behavioral symptoms were asked from 28% to 81% of the questions in the questionnaires

• Cognitive symptoms were addressed by 9% to 44% of the questions

• Emotional symptoms accounted for between 0% and 24% of the questions

• Physical symptoms were only asked about in 3 of the 9 instruments

In questionnaires, a study showed considerable deviations in the assessments of parents, teachers and people with ADHD, with the exception of emotional dysregulation, all existing symptoms, but even more so the frequency of their occurrence.²⁵

Emotional dysregulation (also in ADHD) can be tested with the

• Reactivity, Intensity, Polarity and Stability questionnaire (RIPoSt-40)²⁶

Individual studies found that children with ADHD performed worse on tests with a slow event rate, while their results on exciting, challenging tasks were comparable to those of people with ADHD^{27 28}

It is consistent with this that the results of tests with people with ADHD change when rewards are promised.²⁹ This also indicates that it is not the ability to concentrate or inhibit that is impaired per se, but rather that insufficient activation by “normally interesting” stimuli is the actual key.

In the case of self-assessment questionnaires, response tendencies and unintentional misjudgments can influence the result.
Subjects who were asked to report their daily physical activity showed considerable deviations from the actigraphy measurement, even though they were aware of the actigraphy measurement.³⁰

2. Interviews / instruments for ADHD diagnostics¶

Interviews are questionnaires that are completed by the doctor/therapist conducting the interview. These are usually based very closely on the DSM criteria.³¹ This narrows down the diagnosis in an unpleasant way, as the DSM and ICD only use a very narrow catalog of symptoms.

2.1. Interviews / instruments with preschool children¶

• Behavior Rating Inventory of Executive Function in Preschool (BRIEF-P)³²

2.2. Interviews / instruments with schoolchildren / adolescents¶

• Diagnostic Interview Schedule for Children (DISC-IV)³³
  Recording period 6 months
• Diagnostic Interview for Children and Adolescents (DICA-R)³⁴
• Child and Adolescent Psychiatric Assessment (CAPA)³⁵
  Recording period 6 months
• Schedule for Affective Disorders and Schizophrenia for School-Age Children (K-SADS)³⁶
• Childrens Interview for Psychiatric Syndromes (ChIPS)³⁷
• Swanson, Nolan and Pelham-IV (SNAP IV)
  • 26 items across 18 ADHD and 9 ODD symptom criteria, based on DSM IV.
    Free of charge for clinical use.³⁸ Only available in English.³⁹
• Scale for recording current symptoms of attention deficit/hyperactivity disorder and oppositional defiant disorder according to DSM IV (ADHD-ODD scale)⁴⁰
  • According to Kiddie-Sads-Present and Lifetime Version, K-SADS-PL
• DIVA is also suitable for diagnosing adolescents aged 12 to 17. See below.

2.3. Interviews / instruments for adults¶

2.3.1. Tests for ADHD symptoms in adulthood¶

• Diagnostic Interview for ADHD in adults (DIVA)⁴¹
  • Current: DIVA 5
  • Time required: 1 - 1.5 hours
  • Download for 10 € possible⁴²
    • However, the DIVA 5 evaluation differentiates according to age:
      • Children between 5 and 12 years: ADHD (+), if:
        • at least 6 symptoms either
          • Of inattention (6 in total) or
          • Hyperactivity/impulsivity (6 in total) or
          • Of both inattention and hyperactivity/impulsivity (12 in total) are present.
      • Adolescents between the ages of 12 and 17: ADHD (+) if
        • At least 6 symptoms either
          • Of inattention (6 in total) or
          • Hyperactivity/impulsivity (6 in total) or
          • Of both inattention and hyperactivity/impulsivity (12 in total).
        • And in addition at least 3 symptoms (of these or others) occurred before the age of 12 years
      • Adults: ADHD (+), if
        • At least 3 symptoms of inattention or hyperactivity/impulsivity before the age of 12 years
        • And additionally at least 5 symptoms of either inattention (5 in total) or hyperactivity/impulsivity (5 in total) or both (10 in total)n
• Homburg ADHD Scales for Adults (HASE)
  HASE consists of five individual procedures⁴³⁴⁴
  • Wender Utah Rating Scale - German short form (WURS-K)
    Objective: retrospective diagnosis of childhood ADHD-HI symptoms⁴⁵
    Refers to ages 8 to 10 years. Must be adjusted accordingly after the DSM criteria have been raised to the age of up to 12 years.
    Method: Self-assessment
    Time required: 10 - 15 min.
  • ADHD self-assessment scale (ADHD-SB)
    Objective: To measure the 18 diagnostic criteria of DSM-IV and ICD-10.
    Method: Self-assessment
    Time required: 10 - 15 min.
  • ADHD Diagnostic Checklist (ADHD-DC)
    External assessment scale for experts based on DSM-IV and ICD-10 criteria
    Method: External assessment
    Time required: 10 - 15 min.
  • Wender Reimherr Interview (WRI)
    structured interview with 28 psychopathological characteristics that are particularly important for the diagnosis of ADHD in adults
    The Wender-Reimherr interview is criticized for understating the symptoms of the predominantly inattentive presentation form (ADHD-I)⁴⁶
    Method: Interview
    Time required: 25 - 35 min.
  • Wender-Reimherr self-assessment for adult ADHD (WR-SB)
    new self-assessment scale for ADHD in adults
    Method: Self-assessment
    Time required: 30 - 45 min.
• Integrated Diagnosis of ADHD in Adults“ (IDA-R) test system⁴⁷
  IDA-R summarizes relevant self-assessment and external assessment instruments to enable a time-efficient and reliable diagnosis based on the current DSM standard. It is available as a print and online version. The set consists of a training video and 3 tests:
• ASRS of the WHO
  • Validated short form of the Wender-Utah Rating Scale (WURS-K) for the retrospective assessment of ADHD symptoms in children and
  • A diagnostic interview based on the latest DSM criteria to assess the current symptoms.

2.3.2. Tests for ADHD in childhood¶

In adulthood, the presence of ADHD symptoms in childhood/adolescence must be established.
The WURS⁴⁸ (free, 6 - 10 years) or the WURS-K (for a fee, part of the HASE, 8 - 10 years) can be used for this purpose.
At 86%, the WURS-K shows a diagnostic accuracy for ADHD in childhood that is 10% worse than the WURS⁴⁶

The WURS-K is said to systematically lead to diagnostic problems, as women and girls in particular, as well as men with the predominantly inattentive presentation form ADHD-I, fall minimally below the scores despite otherwise clear ADHD symptoms⁴⁶
The WR-SB self-report questionnaire is also designed not to recognize the predominantly inattentive ADHD-I presentation form⁴⁶
Even if the score is only slightly below the required level, the automated evaluation via the Hogrefe test system determines that the ADHD criteria are not met.

2.4. Live interviews compared to video testing¶

Live interviews and video interviews showed no differences in the results.⁴⁹

2.5. Online self-tests¶

Most of the online self-tests freely available on the internet provide a rough initial assessment. However, pre-testing with such tests distorts the test results of subsequent tests (bias).
However, due to the dramatic lack of resources for diagnosing ADHD and an undeniable lack of knowledge on the part of many doctors and psychologists, the advantages of people with ADHD being able to diagnose it outweigh the disadvantages
the risk of bias is significantly reduced if patients can form their own opinion as to whether a diagnosis makes sense for them.

We have developed our own - quite extensive - online self-test, which showed an agreement of around 93% with existing ADHD diagnoses and around 96% with the CAARS-L. Nevertheless, like any online self-test, it is only an indication and can in no way replace a medical diagnosis. There is also an external assessment base for this. Evaluations are available for both, which can be presented to the subsequent diagnostician, who can then understand in detail how the evaluation came about. This provides an additional perspective on the symptoms.
⇒ ADHD online tests

3. Tests for ADHD diagnostics¶

Attention tests are much more objective than questionnaires.
On the one hand, however, there is a risk that the results may be distorted. Influences can result from training, hyperfocus of a person with ADHD, test anxiety of a person without ADHD or giftedness. The latter points in particular should therefore always be clarified by means of a differential diagnosis.
On the other hand, their diagnostic value is very limited. Barkley warns in no uncertain terms against the use of neuropsychological tests to diagnose ADHD. Neuropsychological tests - even if they test executive functions - can be successfully completed by more than half of people with ADHD and therefore lead to false non-diagnoses. Rating scales, on the other hand, are much better suited to diagnosing ADHD.⁴ Using the NIH Toolbox, Little Man Task, Matrix Reasoning Task and Rey Delayed Recall, one study found a high variance of 31% for ADHD compared to 2.7% for ASD.⁵⁰

3.1. Test procedure for ADHD diagnostics¶

Source, with more detailed explanations: Schmidt, Petermann.⁵¹

3.1.1. Neuropsychological test procedures¶

• Test battery for attention testing (TAP)
• Attention Load Test - Revision (d2)
• Frankfurt Attention Inventory (FAIR)
• Test battery for career starters - concentration (START-K)
• Frankfurt Adaptive Concentration Test (FAKT-II)
• BLAST (Bron/Lyon Attention Stability Test): Computer-aided test to determine task switching problems⁵²
• Cambridge Neuropsychological Test Automated Battery (CANTAB)
  In a study, the CANTAB proved to be unsuitable for the diagnosis of ADHD.⁵³
• Conners’ Continuous Performance Test 3rd Edition (CPT3)
• Conners’ Continuous Auditory Test of Attention (CATA)
  CPT3 plus CATA had a higher sensitivity (82.6%), a higher specificity (76%), a higher positive predictive value (88.8%), a higher negative predictive value (65.5%) and an overall higher correct classification rate (80.6%) than CPT3 or CATA alone.⁵⁴

3.1.2. Individual attention and reaction tests¶

One study found that the Stroop Test, Stroop Plus Test and Perceptual Selectivity Test were good at distinguishing ADHD in adults from non-affected individuals, with the Stroop Test performing best by a narrow margin. However, while the Stroop Test and Stroop Plus Test differed depending on the age of the test subjects, the Perceptual Selectivity Test barely showed any difference across age.⁵⁵ Other studies also showed that the performance of the test subjects in the Stroop Test was age-dependent, with sometimes younger and sometimes older test subjects performing better. In the study mentioned here, both adult persons with ADHD and non-affected people with ADHD performed less well on the Stroop Test as they got older.
The Stroop test is designed to examine selective attention in particular.⁵⁶

3.1.2.1. Stroop Test¶

Aim of the study: selective attention in the network of the dorsal anterior cingulate cortex (dACC) → striatum → thalamus → dACC.⁵⁶

Color word-color interference test.
4 color words (green, red, blue, yellow) are visually displayed in different colors. The color word and the 4 uncolored answer buttons on the right side of the screen below each other are always in the same place. The color words are displayed for 2 seconds, with a dot to be fixed for 0.75 seconds in between. The word and color match in every fourth display, but not in the others. The respondent is asked to name the visual color of the displayed word as quickly as possible.
If the color word and color are different, this is more difficult. People with ADHD have a higher error rate (in %) and a higher reaction time (in ms).⁵⁵

3.1.2.2. Stroop Plus Test¶

Aim of the study: selective attention in the network of the dorsal anterior cingulate cortex (dACC) → striatum → thalamus → dACC.⁵⁶

In the Stroop Plus Test, the structure of the Stroop Test is extended by four colored boxes arranged around the word. Together with the word, an arrow appears between the word and the boxes, pointing to one of the colored boxes. The visually displayed color of the word and the color known from the word do not match in 3 out of 4 trials, as in the Stroop test. Only in every ninth trial do the color, word and displayed color box match. The respondent is asked to name the visually displayed color of the word shown as quickly as possible.⁵⁵

3.1.2.3. Perceptual Selectivity Test¶

Aim of the study: selective attention in the network of the dorsal anterior cingulate cortex (dACC) → striatum → thalamus → dACC.⁵⁶

The Stroop test is presented in the middle of the screen. Four symbols (shape: circles or squares) in different colors (blue and yellow) are displayed around the word, 3 of which show one shape and one the other. In half of the runs, 3 symbols have the same color and one the other, in the other half 2 have one color and 2 the other.
In each of the shapes, a line is displayed that points to 12 o’clock, 1:30 p.m., 3 p.m. or 4:30 p.m. (intended as an hour hand). The test person should only pay attention to the orientation of the line in the symbol that shows the individual shape (which can be horizontal or vertical here) and confirm this as quickly as possible with the assigned button.
This test is designed to measure perceptual selectivity, a subset of selective attention. This term refers to the discriminability of a stimulus, i.e. how effectively the participant can distinguish the target task when confronted with a single stimulus (shape change only) and with two stimuli (shape change and the presence of an irrelevant color).⁵⁵

3.1.2.4. N-back test¶

Objective: Sustained attention, working memory in the network dlPFC → striatum → thalamus → dlPFC.⁵⁶

N is a variable.
In the visual 0-back test, the respondent is shown a number on a screen and asked to press the key that corresponds to the number. In the 1-back variant, the respondent is asked to press the key of the number that was shown before the one just displayed. In the 2-back variant, the respondent is asked for the penultimate number before the number shown. The higher N is, the greater the load on the working memory.

The N-back test can also be performed by playing an acoustic number announcement. There is also a variant in which different fields light up one after the other on a square field and the respondent has to tap the N field previously activated.

3.1.2.5. Stop signal task (SST)¶

The stop signal task is used to measure impulsivity or inhibition.

The respondent is asked to record the results of visual symbols that have two alternative outcomes. For example, a left or right button should be pressed as quickly as possible on arrow symbols pointing to the left or right. After a few unevaluated practice runs, the test person should not press a button when an audio signal sounds at the same time, which sounds irregularly for approx. 25% of the runs. The stop signal sounds with a delay after the stimulus. This delay time can vary between 100 ms and 600 ms.⁵⁷

The following are measured

• Number of directional errors
• Proportion of successful stops
• Response time for Go attempts
• Stop signal response time (SSRT)

The stop signals vary in different passes in order to measure the test results of the stop signal response time to 50 % error in order to achieve a measured value that is as comparable as possible. Here is a Video of the stop signal task on Youtube.

The Stop Signal Task is part of the CANTAB. In a study, the CANTAB proved to be unsuitable for the diagnosis of ADHD.⁵³

One study converted the stop signal task into an application with mouse control instead of buttons, which showed various improvements in the measurements:⁵⁸

• The SSRT shows a weak association with impulsivity, while the measurement of mouse movement shows a strong and significant association with impulsivity
• A machine learning model (weak AI) was able to accurately predict the impulsivity rating of “unknown” participants using mouse movement data from “known” participants
• Mouse movement characteristics such as maximum acceleration and maximum speed are among the most important predictors of impulsivity
• The use of preset stop signal delays leads to a behavior that indicates impulsiveness better than an adaptation of the delay value to previous results (staircase model)

One study found evidence that the performance of stop signal tasks in ADHD reflects impairments in early attentional processes rather than inefficiency in the stopping process.⁵⁹

3.1.2.6. Children’s Color Trail Test (1/2)¶

The Children’s Color Trail Test measures attention, divided attention and speed of mental processing and is used, among other things, to diagnose ADHD.⁶⁰⁶¹

3.1.2.7. Continuous Performance Test (CPT)¶

A 14-minute continuous performance test (CPT), which requires a high reaction speed, shows variables of improved performance with increasing age:⁶²

• Response time (RT)
• RT standard error
• Omission error
• Commitment error
• Signal detection parameters (d’ and beta)

The following in particular are gender-specific

• more impulsive mistakes in men
• lower variability in men
• faster RT in men

3.1.2.8. Digit Span Test¶

The Digit Span Test is part of the Wechsler Adult Intelligence Scale- Revised (WAIS).
The test measures the storage capacity of the working memory for numbers. The test subjects see or hear a sequence of numbers and are asked to reproduce them correctly (forwards or backwards). During the test, the length of the number sequences is increased. The respondent’s number span is the longest number of digits that they can reproduce correctly.
At https://tools.timodenk.com/digit-span-test a Digit Span test can be taken online.

3.1.2.9. Wisconsin Card Sorting Test¶

The Wisconsin Card Sorting Test is available in both electronic and manual form.⁶³

3.1.2.10. Qb test¶

The QbTest combines a continuous performance task (CPT) with a movement tracking system and is intended to support the diagnosis of ADHD. A weak to moderate diagnostic quality was found in children and adolescents.⁶⁴

3.1.3. Test matches¶

• Nesplora Aquarium
  Virtual reality game / test, experimental. It is designed to predict ADHD symptoms in adults and adolescents based on current and retrospective self-reports.⁶⁵
• In another approach, artificial intelligence/machine learning was able to correctly diagnose ADHD in players of an online role-playing game (PlayerUnknown’s Battlegrounds) with an 81% probability.⁶⁶ A generalized anxiety disorder was detected 84.9% of the time.

3.1.4. Virtual seminar room (VSR)¶

One study investigated the use of virtual reality (VR) to provide a more realistic and complex, yet standardized, testing environment. In VSR, a virtual continuous performance task (CPT) was combined with simultaneous visual, auditory and audiovisual distractions. At the same time, head movements (actigraphy), gaze behavior (eye tracking), subjective experience, electroencephalography (EEG) and functional near-infrared spectroscopy (fNIRS) were recorded. Significant differences were found in non-medicated persons with ADHD with regard to⁶⁷

• CPT performance
• Head actigraphy
• Distraction gaze behavior
• the subjective experience
  although no group differences were found in theta-beta ratio (EEG) or dorsolateral prefrontal oxyhemoglobin (fNIRS).

3.1.5. AI test systems: major progress in the lab¶

AI knowledge systems such as chat GPT have been on everyone’s lips since 2023.

Compared to the varying reliability of mental health diagnoses, the research results in the laboratory already show very impressive values.⁶⁸
Nevertheless, the results of such test systems are a long way from actually being usable. The detection rates usually only relate to small databases of 20 to a few hundred data sets (given in n), consisting exclusively of data from people with ADHD and healthy subjects. In practice, however, ADHD can also be distinguished from other mental disorders.

The temporal and qualitative development of the detection rates gives a good impression of the potential of AI diagnostics. The % figures indicate the accuracy, the year figures indicate the publication date of the descriptive publication.

• 99.17 % (2024) in a data set of children with ADHD healthy children using EEG data of the theta band of the frontal and occipital lobe (n = 121)⁶⁹
• 98.77 % (2023) through a new CNN based on fMRI data sets⁷⁰
• 98.7% (2024) using video data with facial, body posture and hand features of adults with ADHD through machine learning (n = 22)⁷¹
  • Accuracy of 98.67 %
  • Precision of 98.01 %
  • Recognition of 98.88 %
• 96.5 % (2024) using the hybrid PUDMO algorithm for the evaluation of EEG data⁷²
• 96 % (2024) by the convolutional neural network CNN model RBP, which was originally developed for the precise classification of brain tumors in medical imaging (n = 3000)⁷³
• 94.5 % (2024) with the LRP algorithm (Layer-wise Relevance Propagation) based on EEG data⁷⁴
• 93.9 % (2024) Frequency-Integrated Visual-Language Network (FIVLNet), a deep learning framework for analyzing MRI scans⁷⁵
• 88 % (2020) using a convolutional neural network (CNN) to analyze EEG data, in particular event-related potentials collected during the flanker task⁷⁶
• 82 % (2023) accuracy for a special AI system for the diagnosis of ADHD. The sensitivity was 64 % and the specificity 99 %. The accuracy was higher than for all other disorders tested with this system⁷⁷
• 79 % (2023) through a combination of 4 machine learning algorithms for analyzing register data.⁷⁸
• 75.6% (2021) using a combination of Convolutional Denoising Autoencoders (CDAE) classification method and Random Forest (RF) algorithms, with a sensitivity of 76.9% and a specificity of 73.1%⁷⁹
• 74.9% (2020) by a multimodal 3D-CNN using gray matter features and fALFF from fMRI⁸⁰
• 69.15 % (2017) using a deep learning model to classify MRI scans⁸¹

Further AI systems for diagnosing ADHD are currently under development.⁸²

3.2. Problems with neuropsychological ADHD tests¶

When testing people with ADHD, it must always be taken into account that the symptoms to be measured are not always and consistently present in people with ADHD. Rewards change the symptom pattern in ADHD.²⁹ In particular, a high motivation of the person with ADHD to participate in the test (intrinsic or through high extrinsic incentives) can distort the test results. This can go so far that the test is negative even though ADHD is present.

3.2.1. People with ADHD perform as well in tests as people without ADHD with the right motivation¶

Motivation is altered in people with ADHD. Extrinsic incentives must be higher than for those without the disorder in order to trigger the same motivation.

Against this background, computer games that aim to measure ADHD could face the problem that the more fun the computer game is, the less meaningful the test results become. One study did not find significantly higher levels of flow and intrinsic motivation in a stop-signal game than in a non-gameified stop-signal test.⁸³

3.2.1.1. No / fewer ADHD symptoms in tests with high motivation¶

3.2.1.1.1. Attention tests¶

In ADHD, it is not the technical ability to pay attention or direct attention that is impaired, but the way attention is directed is subject to different criteria than in those not affected. Attention control in ADHD is subject to a different control system, which is much more dependent on the satisfaction of one’s own needs than in non-affected people. However, this is not selfishness, but an altered control of motivation over which the person with ADHD has no influence.

If personal needs are addressed through intrinsic interest or rewards (which must be higher on average than for people not affected), the attention performance of people with ADHD improves more than that of those not affected.⁸⁴ Ryffel-Rawak describes a typical example.⁸⁵
A meta-study confirms that high rewards greatly improve test scores in ADHD.⁸⁶

In ADHD, deactivation of the default mode network (DMN), as occurs with attention to the environment, is significantly reduced. Personal motivation induced by high rewards equalized DMN deactivation in ADHD, so that it corresponded to that of non-affected individuals. MPH had the same effect.⁸⁷

3.2.1.1.2. Impulsivity (inhibition) can be improved through rewards¶

Impulsivity in ADHD (inhibition ability) can also be influenced by rewards,⁸⁹ up to results equivalent to controls, while the same rewards improved inhibition less in children with brain injuries.⁹⁰ Another study also found identical inhibition ability of persons with ADHD and non-affected people with high rewards.⁹¹ Another study found no improvement.⁹² It would be necessary to check whether the rewards here were possibly too low to arouse personal motivation.

3.2.1.1.3. Reaction times: Reward accelerates reaction times and reduces reaction variance only in ADHD¶

The test results on reaction times in ADHD are inconsistent. Many tests show a reduced reaction time in people with ADHD, while individual tests show an increased reaction time. ⇒ Reduced reaction time with ADHD?

On average, the reaction time of people with ADHD varies more than that of people without ADHD.
⇒ Reaction time variance increased in ADHD

In one study, when rewarded, only the persons with ADHD and their unaffected siblings showed accelerated mean reaction times and lower response variability, but not the controls, while accuracy improved in all 3 groups.⁹³

3.2.1.2. ADHD symptoms more visible in low-demand tests¶

Activating, exciting tasks can cause test results of people with ADHD to correspond to those of controls.⁹⁴ For example, test results of people with ADHD show inconspicuous results when a high test event rate (fast test) is presented, while a low event rate (slow test) shows significant differences.⁹⁵⁹⁶

One study hypothesizes that a slower event rate on tests in people with ADHD causes reduced intrinsic motivation due to their specific motivational characteristics.⁹⁷

The optimal arousal range, in which no under- or overstimulation occurs, is much narrower with ADHD than with non-affected people.
Even more important than the optimal arousal range, however, is the fact that persons with ADHD can direct their attention just as well as people without ADHD if they are personally motivated (example: hyperfocus). This is understandable in light of the stress benefits of altered attention control in ADHD.
⇒ Stress benefits of distractibility, task switching problems and attention problems

In addition to under- and overload, this limited capacity can also exist in terms of time, in the sense that the ability to compensate for under- or overload is limited. One teacher described her perception of a child with ADHD-I to us by saying that she could see how the child “ran full” in the first lesson and then developed the typical ADHD-I symptoms.

3.2.2. ADHD symptoms and relationship to test subject¶

One study addresses how the relationship with the test administrator influences the test results of people with ADHD.⁹⁸

3.2.3. Smoking masks ADHD symptoms¶

Smoking as self-medication increases dopamine levels - albeit only in the short term. It also reduces stress symptoms and irritability. People with ADHD smoke about twice as often as people without ADHD.
Smoking can therefore make the diagnosis of ADHD more difficult.⁹⁹

A study of emotional dysregulation in smokers with ADHD found no differences between those who smoked as usual and those who abstained from smoking for 24 hours.¹⁰⁰
It is well known that withdrawal from alcohol and other drugs requires a period of 2 to 4 weeks so that the receptors downregulated by the high supply of neurotransmitters (dopamine, etc.) can upregulate again. This is responsible for the withdrawal symptoms, among other things. This also applies to nicotine. It is possible that only tests that require nicotine withdrawal of more than 2 to 4 weeks will be able to show a difference.

3.2.4. 116.200 Different ADHD “subtypes¶

One study calculated that there are 116,200 different ADHD subtypes - if each combination of symptoms is considered a separate subtype.¹⁰¹

Against this background, the currently (still?) common test procedures, which (using DSM 5 as an example) are based on 9 characteristics for hyperactivity/impulsivity and 9 characteristics for inattention, of which at least 6 characteristics must be fulfilled in at least one category, should be questioned. People with ADHD with 5 features in both categories would be qualified by DSM 5 as “no ADHD”. Not all doctors realize that the DSM and ICD are merely guidelines and not diagnostic standards - a misunderstanding that Francis Allen, the head of the DSM IV Commission, warned against.
On this basis, we consider Barkley’s and our approach of a diagnosis based on a query of a large number of symptoms to be well worth considering. ⇒ The big ADxS.ORG - ADHD online test

3.2.5. Evaluations by parents and teachers differ significantly¶

One study found that teachers’ and parents’ evaluations of the effects of medication for ADHD did not correlate. These strong differences demonstrate that different sources should be used when evaluating ADHD.¹⁰²

3.2.6. Conclusions¶

For reliable results, tests for ADHD would have to be carried out correctly in different test environments that take into account the degree of underchallenge, appropriate arousal and overchallenge. Furthermore, smoking behavior should be included in the weighting of the test results, which has not been done sufficiently to date. Testing on the basis of all possible ADHD symptoms seems to us to be an option worth considering.

4. Objective measurement methods (biomarkers) for ADHD¶

To date, there is no biomarker in sight that could be used to diagnose ADHD by measuring objective biological or neurological values.¹⁰³

However, measurement methods have already been researched enough to validate and support diagnoses. The advantage of measurement methods is that the result is not distorted by prior knowledge, training or particular motivations (interest, hyperfocus).
However, it is known that people with ADHD “outsource” the functions of disturbed brain areas to other areas of the brain in order to compensate for the deficit. Symptoms are also reduced through coping, e.g. by avoiding situations in which the stressful symptom can occur, or individual symptoms are reduced through intensive training. If only symptoms are asked about, the symptom masked by relocation to other areas of the brain or by coping may not be noticed. This is one of the reasons why tests (including our own online tests) can never be sufficient on their own to reliably diagnose or rule out ADHD.

It is to be hoped that with further refinement of the measurement methods and knowledge about the evaluation of results, a more objective diagnosis than questionnaires and tests will be possible in the foreseeable future.

However, the fundamental problem with measuring biomarkers is that they can only ever provide a snapshot. The results of this snapshot depend on whether the person with ADHD is experiencing acute stress at the time of measurement or not. The usual ADHD diagnosis is therefore correctly based on whether the (stress/ADHD) symptoms exist in the long term, i.e. also outside of acute circumstances that trigger particular stress.

To date, the relevant literature has not yet addressed the extent to which biomarkers can reliably distinguish long-term changes from merely acute stress reactions.

4.1. EEG / QEEG measurement¶

The measurement of QEEG or EEG can support diagnoses. Further information on QEEG and neurofeedback therapy for ADHD can be found at ⇒ Neurofeedback as ADHD therapy In the chapter Treatment and therapy.

A multifactorial 19-channel EEG analysis called “ADHD-AID” reported an ADHD diagnostic accuracy of:¹⁰⁴

• Accuracy: 0.991
• Sensitivity: 0.989
• Specificity: 0.992
• F1 score: 0.989
• Mathew correlation coefficient: 0.982.
• AUC: 0.9958

Older studies reported an ADHD detection rate of an EEG transformer model with an average accuracy of 95.85% and an average AUC value of 0.9926.¹⁰⁵ An EEG classification model with machine learning reported a classification accuracy of 98.28% to 98.86%.¹⁰⁶ Using phase-based analysis, one study preidentified two biomarkers that differentiate ADHD in children from healthy children with 99.174% accuracy:¹⁰⁷

• the subgraph centrality of the phase shift index of brain connectivity within the beta and delta frequency bands
• the node betweenness centrality of the inter-site phase cluster connectivity within the delta and theta bands

In practice, however, people with ADHD do not have to be distinguished from healthy people, but ADHD has to be distinguished from other disorders of unknown composition. This is a much more complex task than all the methods presented so far have been able to solve.

4.1.1. Beta-theta ratio as a diagnostic tool¶

Attempts have been made to use the theta-beta ratio as a diagnostic tool for ADHD.
Although individual studies on this have appeared promising, this diagnostic approach does not yet seem suitable for diagnosing ADHD.

The theta-beta ratio is said to be significantly altered in ADHD.

• Increased power in delta, theta and low-alpha over central parietal regions
• Increased power in low beta in frontal regions
• Increased power in mid-beta over parietal regions.

Our discussions with a neurofeedback therapist revealed some interesting findings:

• Not only in ADHD, but also in a number of other mental disorders, such as depression, Compulsions, trauma or even migraine sufferers, beta increases in a state of relaxation, while it decreases in healthy people when they relax.
  This - characteristic - increase in beta levels during relaxation could possibly explain the symptoms of racing thoughts and sleep problems.
  We conclude from this that the theta-beta ratio in the laboratory environment can at best enable a clear diagnosis to be made as a differentiation of a group of people with ADHD compared to a group of (proven) healthy people. However, it is probably not suitable as a diagnostic tool in real life - for people for whom it is not known whether they suffer from ADHD or another Disorder, or are healthy - because deviations in the theta and beta range occur in a large number of mental disorders and the alternative to the presence of ADHD, unlike in the test environment, is not necessarily “healthy”, but includes the possibility of a number of other mental disorders or tendencies.
• ADHD-HI and ADHD-I have characteristically different theta/beta profiles.
  • In ADHD-HI and ADHD-C (with hyperactivity), theta is typically too low and beta is typically too high
  • In people with ADHD-I (without hyperactivity, dreamers), theta is typically too high and beta is typically too low. Here, the theta-beta ratio should therefore be too low - contrary to the postulation in the studies cited above.
  • In both groups, theta/beta training (relaxation training) proves to be helpful - in ADHD-HI, theta is trained up and beta is trained down at the same time, while in ADHD-I it is the other way round, reducing theta and increasing beta (concentration training). In both cases, it is not just the objective change in the values that is therapeutically effective, but the learned ability to influence the values, even if this results in the values being changed towards average values.

Joint tests with a neurofeedback therapist revealed a significant influence of medication and food (sugar) on the QEEG values.

• Methylphenidate causes greater agitation within the QEEG values within a few minutes. As expected, methylphenidate impeded the theta increase and beta decrease in ADHD-HI targeted by neurofeedback. This is not surprising as MPH is a stimulant. It explains why MPH should be taken in such a way that the effect has worn off by bedtime.
• Sugar (2 chocolate bars within 5 minutes at 90 kg body weight) caused significant changes in the QEEG of an ADHD-HI subject.
  • Within 10 minutes, Beta1 increases considerably.
    The threshold values for theta up / beta down training had to be reduced considerably. The 85 % of the target values achieved before the sugar intake had dropped to 50 %. This means that the ability to relax had decreased drastically.
  • After 20 minutes, all values (theta, alpha, beta1, beta 2, hi-beta) were significantly reduced. Relatively speaking, however, beta 1 was now clearly above SMR. (Beta1 should be below SMR, which is why SMR training (which targets it) is the first step in neurofeedback treatment for ADHD).
  • After 30 minutes, Beta1 had caught up slightly with SMR. However, Hi-Beta was now significantly higher.

There is also the problem that different EEG measurement software products apparently use different calculation methods to determine the beta-theta ratio and therefore produce significantly different results with the same data.¹¹⁴ Therefore, the International Collaborative ADHD Neurofeedback (ICAN) randomized clinical trial used a fixed theta-beta ration cutoff of ≥ 4.5, which had to be measured with the Thought Technology Monastra-Lubar Assessment Suite, 1.5 SD above the norms collected with this system.

• Binaural music also has a significant influence on the change in the QEEG.
  ⇒ Binaural music for ADHD and sleep problems.

One study came to the conclusion that the theta-beta ratio of the EEG in both non-affected and persons with ADHD-C is a reflection of cognitive processing activity and can be measured using the P 300 latency in the acoustic oddball test. In contrast, absolute alpha power did not correlate with P300 latency or amplitude in persons with ADHD-C.¹¹⁵

4.1.2. Changed slope / offset of the 1/f noise in the EEG¶

“1/f noise” in the EEG are arrhythmic signals in the cortex that are typical of ADHD as neural noise. Increased individual reaction time variance is a sign of increased neural noise. MPH improves this.¹¹⁶

In 3- to 7-year-old children with ADHD, a steeper slope and a larger offset were found with regard to the “1/f noise” in the EEG. These data correlated with altered theta/beta ratios. Both values were normalized by medication. In addition, a greater alpha power was found.¹¹⁷

4.1.3. Measurement of evoked potentials¶

Event-related potentials are waveforms in the electroencephalogram (EEG) that are related (correlated) to an observable event (sensory stimulus, movement).
Evoked potentials are event-related potentials in which a test person always receives the same stimulus without further instruction, so that it is purely perceptual.

The measurement of evoked potentials is an objectified diagnostic procedure. Characteristic EEG amplitude curves triggered by stimuli are measured in various regions of the brain typically affected by ADHD. A typical average amplitude curve is determined from a large number of test runs. These EEG courses can be compared with data from non-affected people and data from people with other disorders, which are collected in so-called QEEG databases.
Unfortunately, diagnosis using evoked potentials is time-consuming (4 hours of tests, which are subsequently evaluated) and therefore not cheap. At the Brain and Trauma Foundation Graubünden Switzerland in Chur, a diagnosis based on evoked potentials costs around CHF 1,250 (as of 2015).

The diagnostic accuracy of measuring evoked potentials is growing rapidly. While Strehl et al cite studies from 2005 with a (still unsatisfactory) diagnostic accuracy of 70 to 80 %, Müller et al 2011¹¹⁸ already claim 89 % diagnostic accuracy: from a group of 212 adults with 106 persons with ADHD, 89 % of those affected were correctly diagnosed using a 19-channel system through automatic evaluation of EVP. Models with machine learning achieve 94 %¹¹⁹
However, these results were determined in laboratory situations in which only ADHD could be distinguished from non-affected individuals. In real-life diagnostics, ADHD can be distinguished from a variety of other disorders. It remains to be seen when this will be possible in practice using such models.

By comparison, trained diagnosticians and experienced clinicians achieved a diagnostic agreement of 88%¹²⁰

One study found no significant differences in evoked potentials between twins with and without ADHD in a continuous performance task.¹²¹

A meta-analysis of 52 studies with 3,370 subjects on early (P100, N100, P200, N200, ERNNe) and late (P300, Pe, CNV) evoked potentials found in ADHD¹²²

• Shorter Go-P100 latencies
• Smaller Cue-P300 amplitudes
• Longer Go-P300 latencies
• Smaller NoGo P300 amplitudes
• Longer NoGo P300 latencies
• Smaller CNV amplitudes
• Smaller Pe amplitudes.

with considerable heterogeneity of the results and moderate effect sizes (d<0.6).

Another study came to the conclusion that evoked potentials show very different correlations with symptoms depending on the age of the test subjects (childhood or adolescence).¹²³

The mismatch negativity (MMN) is a negative component of the event-related response in an EEG signal that is triggered by a perceptible change in a repetitive aspect of auditory stimulation (e.g. stimulus pitch, stimulus duration).¹²⁴
Children with ADHD showed reduced mismatch negativity (MMN) amplitudes in response to two blocks of duration- and ISI-based deviants:¹²⁵

• MMN amplitude measurements:
  • Fz
    • ADHD: -1.2097 ± 0.2938 (continuous block); -0.8553 ± 0.4423 (ISI block)
    • Controls: -1.8325 ± 0.3689 (continuous block) and -2.0855 ± 0.3802 (ISI block)
  • Cz
    • ADHD: -1.2515 ± 0.3261 (continuous block) and -0.9367 ± 0.3432
    • Controls: -2.1319 ± 0.4445 (continuous block) and -2.7561 ± 0.4883
• MMN latencies
  Children with ADHD showed longer MMN latencies in both experimental blocks, indicating atypical responses.
  • Fz:
  • ADHD: 239.68 ± 5.059 (continuous block) or 226.88 ± 4.885 (ISI block)
  • Controls: 228.56 ± 6.584 (continuous block) or 213.56 ± 4.153 (ISI block)
  • Cz
    • ADHD: 234.40 ± 5.741 (continuous block) and 231.44 ± 5.464 (ISI block)
    • Controls: 227.52 ± 6.710 (continuous block) and 218.00 ± 5.261 (ISI block)

4.1.4. Measurement of rsEEG¶

The measurement of 14 resting state EEG parameters was able to identify the participating people with ADHD with an accuracy of around 85% in a process optimized by machine learning.¹²⁶ As it is not only possible to diagnose healthy individuals in the wild, but also other disorders, it is questionable whether the results will be accurate enough to be useful in practice.

4.1.5. Measurement of non-linear EEG values¶

According to a study, a measurement of non-linear EEG values showed a better diagnostic quality of ADHD than other EEG diagnostic methods.¹²⁷

4.1.6. Phase space reconstruction of the EEG¶

One study found that phase space reconstruction of the EEG is very good at distinguishing ADHD from non-affected individuals. ¹²⁸ For diagnostic use, however, a method must also be able to differentiate well between other disorders.

4.1.7. Gamma levels reduced in ADHD¶

One study reported elevated resting gamma levels in adults with ADHD in the 30 to 39 Hz range (gamma1), but not in the 39 - 48 Hz range (gamma2). Resting gamma1 power increased with age and was significantly lower in ADHD than in control subjects in early adulthood.¹²⁹

4.1.8. EPSPatNet86: 8-point EEG measurement on 85 wavelets¶

A study of 85 EEG wavelet factors was able to correctly classify 87% of people with ADHD using machine learning.¹³⁰ It remains to be seen what the recognition rate will be for an open group of test subjects.

4.1.9. EEG analysis using VMD-HT¶

One study used VMD-HT and other secondary EEG characteristics to distinguish between 61 people with ADHD and 60 healthy controls:¹³¹

• an accuracy of 99.81 %
• a sensitivity of 99.78 %
• a specificity of 99.84 %
• an F-1 measure of 99.83 %
• a precision of 99.87 %
• a false detection rate of 0.13 %.
• Detection rate for ADHD of 99.87 %
• Detection rate for healthy controls of 99.73 %

These impressive figures will have to be proven in the real world when not only persons with ADHD and healthy controls, but also people with other disorders are tested.

4.1.10. Brain complexity¶

An analysis of brain complexity in ADHD, including using EEG, found that brain complexity is increased in children with ADHD (with the increase being weaker than in schizophrenia (positive traits) and significantly weaker than in depression) and decreased in adults with ADHD (with the decrease being weaker than in autism and significantly weaker than in dementia).¹³²

4.2. Functional near-infrared spectroscopy (fNIRS)¶

A prospective study of 30 boys using fNIRS of the forehead while performing mental arithmetic tasks was able to identify almost 100 % of the 15 boys with ADHD.¹³³ So far, this is a purely experimental approach.
Another study found no differences by fNIRS in ADHD⁶⁷

4.3. Genetic testing¶

To date, there are no usable genetic tests for the diagnosis of ADHD.
However, initial voices are now (2020) in favor of integrating certain genetic tests (here: array CGH) into the standards of ADHD diagnostics.¹³⁴

There are several difficulties for genetic diagnostics in ADHD:

• ADHD is usually not caused by individual gene variants, but by the interaction of a large number (several hundred to thousands) of gene variants (⇒ gene candidates in ADHD) Gene candidates for ADHD)
• The (epigenetic) expression of genes (e.g. through early childhood or chronic severe stress) can also change the gene effect independently of the gene variant.
• It can be assumed that different combinations of the genes and forms of expression under consideration coincide in different persons with ADHD, but not all genes that contribute to the dopamine balance being disturbed, for example.
• There is not yet a complete set of candidate genes, which is why there is no genetic test for ADHD. We have collected over one hundred and fifty gene candidates.
  ⇒ Gene candidates for ADHD.
• Genetic tests are still too expensive to be able to test the required number of genes.
  It is possible that genetic tests will become so affordable in the coming years that they can also be used for diagnostic purposes - and subsequently to adapt individualized treatment.

One study investigated miRNAs of extracellular vesicles in serum. A longitudinal analysis examining changes in miRNA expression over time between four groups with different diagnostic trajectories (persistent diagnosis, first onset, remitted and typical development/control) found no statistically significant results. In the cross-sectional analysis, miR-328-3p was found to be upregulated in only one of 2 ADHD groups. These miRNAs may regulate the expression of genes associated with these traits in genome-wide association studies¹³⁵

4.4. Endocrine and physical biomarkers¶

4.4.1. Measurement of cortisol levels¶

The cortisol value has two meanings:

• The basal = tonic = long-term value represents the basic level, which changes rhythmically throughout the day (circadian rhythm)
• The phasic = short-term value represents a response reaction to an acute stressor

4.4.1.1. Measurement of the basal cortisol level¶

The basal cortisol level is lower in people with ADHD than in those not affected because the stress load is long-term. In the case of short-term stress, the basal cortisol level initially rises.

This difference could theoretically be used to differentiate between an acute stress reaction (increased cortisol levels) and a collapsed HPA axis regulation (reduced levels) - if the individual fluctuations between people within a group were not greater than the increase or decrease in cortisol levels compared to healthy levels.

According to this hypothesis, however, an individual change in cortisol levels upwards or downwards could be determined if these were recorded regularly (annually) from the earliest age (in children: on the occasion of standard examinations).
Without historical values of the basal cortisol level, however, such a measurement is useless.

In addition, a measurement of the morning cortisol awakening response (CAR) could provide information about the state of the HPA axis. The CAR is a persistent increase in cortisol levels that occurs 20 to 40 minutes after waking up.

A comparative graphical representation of the cortisol profiles of healthy, acutely stressed, chronically stressed, partially burned out and fully burned out people can be found in Bieger.¹³⁶

However, here too there is the difficulty that without individual comparative data, an assessment of the 24-hour picture of cortisol values is barely diagnostically usable.

A measurement of cortisol in hair (which reflects long-term levels) showed that low cortisol levels in preschool children predicted the expression of ADHD.¹³⁷
This could possibly be the result of a long-term stress reaction. The third phase of stress development (resistance phase) is typically characterized by a collapse of basal cortisol levels. The fourth phase (exhaustion phase) is then characterized by a breakdown of the neurotransmitter systems. More on this at ⇒ Resistance phase In the section ⇒ The stress response chain / stress phases of the article ⇒ The human stress system - the basics of stress.

However, changes in basal cortisol levels are not specific to ADHD and are therefore barely useful for ADHD diagnosis.

4.4.1.2. Measurement of the phasic cortisol response to psychological stressors¶

The phasic cortisol response can be used to determine the cortisolergic subtype of ADHD.

ADHD-I is typically associated with an elevated cortisol response compared to unaffected individuals, ADHD-HI with a flattened cortisol response compared to unaffected individuals.

The differences are relevant for treatment. In people with ADHD-I, SSRIs should be used with caution. In ADHD-HI, low-dose SSRIs (2 to 4 mg, i.e. 1/5 to 1/10 of the level used in depression) could potentially improve impulsivity, allowing lower dosing with stimulants.

The Trier Stress Test (TSST) is typically used as a psychological stressor.
This is probably not suitable for a (even annually) repeated examination in view of the expected habituation.

4.4.2. Dexamethasone/ACTH/CRH test?¶

A dexamethasone/ACTH/CRH test can be used to determine whether there is permanent dysregulation at individual levels of the HPA axis.

If ADHD is characterized by a permanent dysregulation of the stress regulation systems, above all the HPA axis, it should be possible to prove the individual dysregulation by testing the HPA axis reactions (changes in the levels of the stress hormones CRH, ACTH, cortisol to acute stressors). At the very least, such tests should provide informative indications for the individual differentiation of subtypes.

Dexamethasone is a glucocorticoid that selectively binds to the glucocorticoid receptors and should thereby trigger the downregulation of the HPA axis (after a stress reaction has occurred). If this downregulation does not occur, this is a strong indication of a disorder in the shutdown of the HPA axis.

More on this at ⇒ Pharmacological endocrine function tests.

4.4.3. Mineral analysis¶

By analyzing zinc, lead, copper, cobalt and vanadium from teeth, one study was able to create an impressively clear distinction between non-affected people, people with ADHD, people with ASD and people with comorbidities.¹³⁸

4.4.4. Axonal damage to the white matter¶

A study of 50 untreated persons with ADHD compared to their unaffected twins and 50 control subjects found higher axonal diffusivity in the ADHD sufferers in the¹³⁹

• Perpendicular fasciculus
• Superior longitudinal fasciculus I
• Lateral corticospinal tract
• Corpus callosum

The values correlated significantly (except in the perpendicular fasciculus) with ADHD symptoms such as inattention and working memory problems and were intermediate between those of people with ADHD and non-affected twins. Axial diffusivity is a marker for the undamaged condition of axons.

4.4.5. 24-Hour movement profiles¶

One study claims to have achieved a diagnostic accuracy for ADHD-C of over 97% by evaluating neural network analyses of 24-hour movement profiles.¹⁴⁰¹⁴¹

4.4.6. Facial features¶

4.4.6.1. Facial morphology in ADHD¶

One study concluded that there may be a close relationship between ADHD and nasal width, ear length and upper face depth, which could be related to genetic signaling processes and a close relationship between the brain and face formation process in the embryonic period.¹⁴²

4.4.6.2. Facial morphology in ASD¶

A study reports on subtle phenotypic facial morphologies in ASD.¹⁴³

4.4.7. Analysis of MRI brain images¶

Optimized machine learning was able to distinguish very well between ADHD and controls and between persistent and remitting ADHD in young adults using MRI neuroimaging. Relevant features of ADHD compared to controls were identified as:¹⁴⁴

• Nodal efficiency in the right inferior frontal gyrus
• Functional connectivity between brain regions right medial frontal and inferior parietal
• Volume of the right amygdala

The remission of inattention and hyperactivity/impulsivity correlated with

• Higher nodal efficiency right medial frontal
• Reduced functional connectivity between right medial frontal and inferior parietal brain areas

4.4.8. Analysis of urine values (-)¶

A functional analysis of urine values for the diagnosis of ADHD has not yet been reported. One study also found no connection between urine values and ADHD in dogs.¹⁴⁵

4.4.9. Analysis of eye values¶

4.4.9.1. Electroretinography (ERG)¶

One study found evidence of gender-specific biomarkers in electroretinography in ADHD.¹⁴⁶

4.4.9.2. Pupillometry¶

Pupil diameters at rest are a biomarker for tonic noradrenal infiring, pupil changes during tasks and in response to stimuli are a biomarker for phasic noradrenal infiring. Find out more at* Tonic and phasic noradrenaline* in the article Noradrenaline in the chapter Neurological aspects of ADHD.
One study achieved a sensitivity of 77.3% and a specificity of 75.3% in the diagnosis of ADHD compared to a control group using a machine learning method from pupil measurements.¹⁴⁷

4.4.9.3. Eye tracker: Duration of target fixation¶

The investigation of distractibility by recording and analyzing eye movements during a task-irrelevant distraction showed a significant correlation between the duration of target fixation and the attention problems reported by the parents (p < 0.001).¹⁴⁸ Other studies also report diagnostic benefits of measuring eye movements during a continuous performance task ¹⁴⁹¹⁵⁰

5. Diagnostic guidelines¶

The most important guideline for ADHD diagnosis in Germany is the Interdisciplinary evidence- and consensus-based S3 guideline “Attention Deficit Hyperactivity Disorder (ADHD) in children, adolescents and adults (AWMF 028045).
Guidelines for the diagnosis of ADHD recommend the following diagnostic procedure:¹⁵¹

5.1. Psychiatric anamnesis¶

Assessment of the individual problem situation, taking into account comorbid disorders, the developmental history of the person with ADHD and their family.

5.2. Differential diagnosis¶

5.2.1. Exclusion of organic causes¶

A differential diagnosis should be carried out in parallel to the ADHD diagnosis to ensure that symptoms do not result from other dominant organic causes.
More on this at ⇒ Differential diagnosis of ADHD

5.2.2. Exclusion of other psychological causes¶

For the differential diagnosis of depression, see ⇒ Depression and dysphoria in ADHD

5.3. Interview with parents/confidants¶

Interviews on retrospective and current symptoms and the use of standardized assessment scales can help to record current symptoms and symptoms in childhood.

5.4. Primary school reports¶

People with ADHD often have a poor long-term memory and therefore have few tangible memories of their childhood.

The head marks / behavioral marks / individual assessments in primary school reports are often helpful in reconstructing the behavior of people with ADHD in childhood.
Some people with ADHD no longer have these certificates. We have received alarming reports that some doctors have refused to diagnose such cases. Of course, this is in no way acceptable:

• DSM and ICD require first symptoms by the age of 12, which is outside primary school age. Barkley also assumes a first onset up to the age of 18.
• It is therefore not appropriate to rule out a diagnosis solely on the basis of inconspicuous primary school reports.
• A high level of intelligence or a high compensatory willingness to perform can make people with ADHD appear inconspicuous in elementary school.
• Girls are also more adapted and often do not stand out as people with ADHD. Women often develop psychological problems at a later age than boys due to their different sex hormone development. More on this under Gender differences in ADHD.
• In our opinion, the current DSM and ICD criteria still overrepresent a classic boy’s ADHD with hyperactivity.
• In addition, some teachers formulated their assessments in a rather friendly way. At the time, no teacher was aware that their assessment would one day be used as a diagnostic measure.

As an alternative to primary school reports, reports from parents, relatives, school friends or graduation newspapers, which often contain very accurate characterizations of the persons by classmates, can also make a contribution.
The absence of primary school reports must never be the (sole) reason for refusing a diagnosis, as no one is obliged to keep these reports. Accordingly, primary school reports should be viewed with caution. In both positive and negative cases, they are an indication that contributes to the overall picture, but are by no means the only decisive “proof”.

5.5. Standardized survey of ADHD symptoms¶

Use of standardized procedures for the detailed assessment of relevant symptoms and their severity.

5.6. Test psychological performance diagnostics¶

Use of procedures to determine the general cognitive performance level.
See above for a warning about this.