SCT - Sluggish Cognitive Tempo / CDS - Cognitive Disengagement Syndrome

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

CDS (Cognitive Disengagement Syndrome) (designation until 2022: SCT, Sluggish Cognitive Tempo¹ ) was previously regarded as a kind of sub-case or extreme case of ADHD-I. This view has since become outdated. This view is now outdated. CDS / SCT is a disorder in its own right and occurs in around 25 to 50 % of people with ADHD, both with and without comorbid ADHD. CDS / SCT is not yet an official disorder according to the DSM.
In the presence of ADHD comorbidity, CDS / SCT appears to occur just as frequently in persons with ADHD-HI as in those with ADHD-I.

We consider the term “slowed thinking” or “sluggish cognitive pace” to be inaccurate and inappropriate in relation to CDS / SCT. Rather, we perceive a slower decision-making process. The ability to think quickly is fundamentally present; we consider - as an unverified hypothesis - an excessive blockade of the PFC by noradrenaline and possibly other neurotransmitters via the alpha-1 adrenoceptor to be possible.

CDS / SCT is characterized by various symptoms, including fatigue, hypoactivity, daydreaming, concentration problems, poorer sleep quality, increased daytime sleepiness, lower memory performance and slower information processing speed.

CDS/SCT can be diagnosed with valid questionnaires and shows specific neurophysiological features. CDS/SCT can affect various aspects of life, including occupational performance and social withdrawal, and is best treated with multimodal therapy. Atomoxetine has shown significant improvement in CDS/SCT symptoms, while SCT people with ADHD are more often reported to be non-responsive to methylphenidate.

• 1. Symptoms of CDS / SCT
• 2. CDS / SCT as an independent Disorder
• 3. Neurophysiological characteristics of SCT
• 4. Medication for SCT

1. Symptoms of CDS / SCT¶

In the following list of CDS / SCT symptoms, the numbers indicate how frequently the respective symptom occurs in CDS / SCT according to Becker et al.². Lee et al.³ also name several of the symptoms as typical for CDS / SCT:

• Quickly tired or exhausted 1.02
• Low activity level, hypoactivity 0.97
• Stares into space 0.96
• Dozy, sleepy, yawning (during the day) 0.95
• Forgets what he/she wanted to say 0.94
• Inertia, slow movements 0.92
• Quickly confused 0.91
• Lost in the fog 0.89
• Daydreams 0.88
• Loses the thread of thought 0.86
• Slow thinking 0.82
• Quickly gets confused 0.85
• Gets lost in thought 0.81
• Switch off mentally 0.82
• Difficulty expressing thoughts 0.78
• Often considerable decision-making difficulties (sluggish - in our experience)
• Social seclusion⁴⁵

A comprehensive review article found 13 independent and distinct symptoms for CDS / SCT from ADHD, but not distinct enough to be used diagnostically.⁶

One study found the Adult Concentration Inventory (ACI) to be suitable for diagnosing CDS / SCT. ⁷ CDS / SCT was clearly associated with:

• Stronger internalizing symptoms
• Time management and self-organization difficulties
• Poorer quality of sleep
• Shorter sleep duration
• Lower sleep efficiency
• More daytime sleepiness.

CDS / SCT is not synonymous with reduced cognitive performance. There are highly gifted people with ADHD / SCT. This is consistent with the finding that CDS / SCT does not correlate with slow processing speed.⁸

The slower cognitive performance specific to the sluggish/underarousal subtype does not mean that intelligence is reduced to the same extent. This means that CDS / SCT is not simply the result of reduced intelligence. We know several people who we perceive as CDS / SCT who have a PhD or are otherwise highly intelligent or even highly gifted. Rather, it seems as if decision-making processes are slowed down or made more difficult. Conversely, a high IQ could mitigate the symptoms of CDS / SCT. One study confirms this.⁹

The ADxS.org online SCT test (as of September 2022) clearly showed a negative correlation between CDS / SCT symptoms and the highest IQ test score given.

IQ	Subjects (n)	CDS / SCT symptoms (out of 26)
150 and higher	7	13.6
140 - 149	54	13.9
130 - 139	158	15.2
120 - 129	162	15.5
110 - 119	88	15.8
100 - 109	33	16.1
90 - 99	15	16.9
80 - 89	8	16.3

A total of 78 (out of 381) subjects with an IQ of 120 and above had 20 CDS / SCT symptoms and more (out of 26).

Out of a total of 2039 subjects, only the 1640 subjects who stated that they did not have ADHD or who stated that they were not taking ADHD medication were included. Of these, 524 had reported their highest IQ test score.
It can be assumed that subjects with lower IQ scores reported these less frequently. The values in the two IQ groups below 100 should be viewed with caution due to the low number of test subjects.
The overall results are limited by the fact that the subjects took part in the SCT online test linked to ADxS.org out of their own interest.
The massive overrepresentation of high IQ scores is probably due to the high participation rate of members of Mensa e.V. Germany, an association for the highly gifted (IQ 130 and above).
Data as of September 2022 (c) ADxS.org

The term Sluggish Cognitive Tempo therefore does not really seem appropriate. Barkley also disagrees with the term SCT.¹⁰ SCT was renamed CDS (Cognitive Disengagement Syndrome) in 2022. In our opinion, Sluggish Decisioning Might be more appropriate.

Our impression is that people with ADHD fail particularly often as self-employed persons.

2. CDS / SCT as an independent Disorder¶

CDS / SCT was previously described as an extreme manifestation of the ADHD-I subtype or an ADHD-I-like type with slowed cognitive performance.¹¹

However, an increasing number of studies are coming to the conclusion that SCT is a separate and distinct Disorder from ADHD.^{12131415161718192021222324} Strong distinctiveness from ADHD-I was found for 13 of the 15 SCT symptoms.²⁵²⁶

A study with n = 1024 subjects found that 40% with ADHD showed increased CDS symptoms, while 60% with CDS showed an increased risk of ADHD.²⁷

2 studies found evidence that SCT could be considered a group of symptoms that occur in various mental disorders.²⁸ When ADHD, depression, anxiety disorder, sleep disorders and alcohol and cannabis abuse were removed, less than 5% of subjects were left with high levels of SCT.²⁹
Children with ADHD, ASD or ASD+ADHD (AuADHD) showed similar CDS symptom scores. However, AuADHD children showed stronger cognitive CDS symptoms than children with ADHD alone. Both the general CDS traits and the cognitive CDS symptom subgroup were associated with greater social difficulties regardless of diagnosis, particularly associated with social withdrawal, higher levels of repetitive behaviors, and more sensory sensitivities.³⁰

A meta-analysis of 9 studies found acceptable to excellent reliability and high structural validity (high loading on an SCT factor and low loading on an ADHD-HI inattention factor) for the majority of SCT items.¹⁴

A large study of over 2,000 families found that in children, only 48% of those with SCT also had ADHD and only 35% of those with ADHD-HI also had SCT. The persons with SCT without ADHD had higher levels of anxiety, depression, shyness and sleep disturbances than those with ADHD without SCT. In contrast, people with ADHD without SCT had greater executive functions deficits and more frequent ODD than those with SCT. SCT and ADHD did not differ in terms of friendships or social or academic impairment.³¹

The Sluggish Cognitive Tempo Self-Report Scale is a valid and reliable self-report scale for the diagnosis of SCT.³²

However, SCT and ADHD appear to have considerable comorbidity. One report suggests that 30 to 63% of people with ADHD-I also have significant SCT symptoms.³³³⁴

Barkley already argued in the early 2010s that SCT was a separate Disorder, which has since been confirmed. In the early 2000s, however, he had also argued that ADHD-I was a separate disorder from ADHD-HI, which has not proved to be the case.

The previous results of the ADxS.org online questionnaire on SCT (as of September 2022) also indicate that although SCT has a high correlation with ADHD overall, it is largely independent of the ADHD-HI / ADHD-C or ADHD-I subtypes. The mean scores of the n = 180 subjects with ADHD-HI / ADHD-C and the n = 241 subjects with ADHD-I are almost identical (ADHD-HI / ADHD-C: 15.4; ADHD-I: 16.9 out of a possible 26 SCT symptoms when assessed as they are when not taking ADHD medication). When persons with ADHD rated themselves as they are when taking ADHD medication, ADHD-HI sufferers had 13.5 symptoms (n = 52, minus 12.3%), while ADHD-I sufferers had 15.4 symptoms (n = 62, minus 8.9%). This suggests that ADHD medication may also have some positive influence on SCT symptoms and that this is greater in people with ADHD with hyperactivity.
In contrast, the n = 33 participants who stated that they definitely did not have ADHD or SCT achieved an average SCT score of 12.5. To date, no participant has stated that they definitely have SCT and no ADHD. This is not surprising given the unfamiliarity of the disorder.

Men achieved an average of 15.7 symptoms (n = 713), women an average of 15.4 symptoms (n = 1,250) out of 26 possible symptoms.

Recent research shows that SCT is thought to differ from ADHD-I in the following ways:

• SCT appears to correlate significantly more frequently than ADHD-I with
  • Later withdrawal from addictive substances¹⁸
  • Internet addiction and internet gaming disorder³⁵
  • Fear^{1718 31}
    • In contrast, one study found no correlation between SCT and anxiety symptoms.²³
  • Depression^3617183123
  • Neuroticism³⁷
  • Increased BIS³⁷
  • Increased BAS fun-seeking³⁷
• SCT appears to be even more strongly associated with later internalizing behaviors than ADHD-I.¹⁷¹⁸²⁵
• SCT is said to correlate (differently or more strongly than ADHD-I) with later shyness¹⁸³¹ or internalizing symptoms¹⁷ as well as lower extraversion³⁷.
• While externalizing symptoms were associated with hyperactivity / impulsivity symptoms of ADHD-HI in one study, internalizing symptoms were significantly correlated with SCT in children and adolescents with ADHD. Although social withdrawal was statistically significantly correlated with ADHD-I and inattention (compared to ADHD-HI), this relationship was mediated by the severity of SCT.³⁸
• SCT, like ADHD-I, is said to correlate with later social difficulties,¹⁷¹⁸ but this has not been confirmed by other studies.³¹
• According to one study, SCT shows even greater social withdrawal than ADHD,³⁹⁴⁰ which another study only partially confirms.³¹
• ADHD-I correlated with later poorer math performance and slower processing speed, while SCT more consistently predicted later poorer reading performance.¹⁸
• SCT correlated (unlike other ADHD symptoms) with suicidal tendencies, which in turn correlated with depression.⁴¹²⁵
• SCT showed lower memory performance than ADHD-I and non-affected individuals.⁴²
• Motor speed and reaction times
  • SCT showed not quite as reduced psychomotor speed and a better neurocognitive index compared to ADHD-I.⁴²
  • SCT showed faster reaction times than ADHD-I.⁴²
  • Slower psychomotor speed and longer reaction times correlated with the degree of inattention.⁴²
  • In contrast to ADHD, the variance in reaction speed is not increased in SCT⁴³
  • The unimpaired variance in reaction times at least tends to be consistent with a report that SCT showed less impairment in executive functions (like reaction time variance mediated by working memory) than ADHD.³¹
• SCT should, unlike ADHD
  • Occur equally frequently in men and women⁴⁴
  • Occur just as frequently in adults as in children and adolescents, even if it occurs somewhat later than ADHD. There is therefore no partial disappearance of symptoms in a subgroup of people with ADHD.⁴⁴
  • In contrast, a 7-year longitudinal study of 639 twins found that SCT is usually short-lived (1 - 2 years) and has no lasting detrimental effects on academic achievement.¹⁷
• SCT showed deviations in HRV compared to ADHD, which could indicate problems with arousal.⁴⁵ Based on the symptoms of CDS, we suspect strong correlations with arousal impairments.
• SCT showed reduced conscientiousness.³⁷
• People with SCT who also have ADHD are said to be particularly frequent MPH nonresponders. In particular, elevated SCT sluggish/sleepy factor values are said to indicate MPH nonresponding. In contrast, neither increased SCT daydreamy symptoms nor the ADHD subtype (ADHD-HI or ADHD-I) differed in the MPH response rate (which argues against the hypothesis of SCT as a subtype of ADHD-I).⁴⁶
• SCT, like ADHD, begins in early childhood, although in SCT symptoms increase moderately after the age of 5, while inattention remained more constant.⁴⁷ SCT was distinguishable from ADHD thereafter, although highly correlative. Lower parental education correlated with higher teacher ratings of SCT. African Americans had higher inattention and lower teacher SCT ratings.
• Unlike ADHD-I, SCT is said to have no features of emotional dysregulation.²⁵
  • CDS correlated with anxiety and depression symptoms, but not with inattention or emotional dysregulation⁴⁸
• In a comprehensive study, SCT symptoms correlated with more frequent⁴⁹
  • Mind wandering
  • Brooding
  • Daydreaming.
    The study further found initial empirical evidence of a unique and robust association between SCT symptoms and non-task-related thinking, while suggesting that the link between ADHD-HI and mind-wandering may be less robust than previously thought.

• SCT is unremarkable in relation to time representation, repetition of non-words and recall of sentences. Instead, SCT appears to be more closely associated with features of a social (pragmatic) communication disorder.⁵⁰

One study found elevated CDS symptoms in 10% of participants and elevated ADHD symptoms in 9.2%. Of the probable ADHD cases, 40% had elevated CDS symptoms, while 60% of the cases with elevated CDS symptoms were at increased risk of ADHD²⁷
Subjects with elevated CDS and ADHD symptoms also had the highest scores for emotional dysregulation and alexithymia. Regression analyses showed that CDS symptoms predicted emotional dysregulation (47%) and alexithymia (32%) better than ADHD scores (emotional dysregulation: 36%, alexithymia: 23%).²⁷

3. Neurophysiological characteristics of SCT¶

• The specific SCT symptoms (sluggish, underarousal) could be caused by a noticeable deficit in the uptake of dopamine and noradrenaline.¹¹
• SCT is thought to correlate with inactivity in the superior parietal lobe (SPL).³³
• Sluggish Cognitive Tempo is said to correlate with attention problems, but not with hyperactivity or aggression problems. Sleep problems are also said to be less frequent.⁵¹
• Sluggish Cognitive Tempo - unlike ADHD - is not conspicuous in the frontal and frontocentral theta-beta ratio of the EEG.⁵²
• According to a study, SCT correlates with impaired information processing capacity and slower (visual) information processing speed.⁵³
  Another study found no correlation between SCT and reduced information processing speed, but a correlation with reduced working memory speed and increased inhibition speed. A combination of slowed working memory and accelerated inhibition was therefore suspected.⁵⁴
• A high working memory load significantly impairs information processing speed. Nevertheless, in ADHD, manipulations of working memory were found to impair information processing speed just as little as vice versa. This suggests that working memory impairments and information processing speed impairments in ADHD are caused by different areas of brain function.⁵⁵
• An interesting report mentions partial brain sleep as a possible cause of some SCT symptoms or mind wandering.⁵⁶
• Sleep problems are highly correlative with SCT/CDS⁵⁷
• Adolescents with SCT completed the Wechsler Symbol Search and Coding subtests and the Grooved Pegboard Test. Their parents did not report any symptoms related to symbol search or coding scores for the persons with ADHD, while the persons with ADHD themselves reported significantly decreased coding scores. Both parents and persons with ADHD consistently reported symptoms that correlated significantly with slower grooved pegboard time. The hypothesis is that SCT correlates more clearly with performance on the processing speed task as motor demands increase.⁵⁸
• A study of children with ADHD aged 8 to 12 years measured SCT symptoms in relation to autonomic nervous system responses under social and cognitive stress. Respiratory sinus arrhythmia (RSA) and skin conductance level (SCL) reactivity were measured. SCT symptoms did not correlate with RSA reactivity in any stress variant. In social rejection stress, greater SCT symptoms correlated with greater SCL reactivity. This pattern was independent of ADHD-HI symptoms, internalizing symptoms, medication status, or gender. The authors conclude that there is a link between SCT symptoms and sympathetic nervous system reactivity and greater activation of the BIS.⁵⁹

Among 169 children and adolescents with spina bifida (SB, open back), 18% were found to have SCT. The study replicated the 3-factor structure of SCT proposed by Penny with the components slow, sleepy and daydreaming. Slow overlapped strongly with inattention, sleepy and daydreaming differed significantly from inattention and internalizing symptoms. A myelomeningocele (congenital malformation of the spinal cord due to lack of closure of the neural tube with open vertebral arches and protrusion of the dural sac) and the presence of a shunt (short circuit connection with fluid spillover between normally separate vessels or cavities) correlated with more severe SCT symptoms.⁶⁰

4. Medication for SCT¶

• In one study, atomoxetine significantly improved 7 out of 9 symptoms of the Kiddie-Sluggish Cognitive Tempo Interview (K-SCT) in SCT. The symptom improvement in SCT was completely independent of ADHD symptoms.⁶¹ This also suggests that SCT is an independent disorder or has an independent cause of disorder and can coexist with ADHD.
• According to one study, people with SCT are particularly frequent MPH nonresponders; in contrast, ADHD-HI and ADHD-I did not differ in the MPH response rate in this study, which is controversial.⁴⁶
• One study found an improvement in SCT symptoms with MPH only in relation to the school environment. Daydreaming and oppositional behavior correlated with a lower MPH response in SCT.⁶²
• The results of the ADxS.org SCT online test suggest that ADHD medications may provide some improvement in SCT symptoms (see above).