SCT (Sluggish Cognitive Tempo) / CDS (Cognitive Disengagement Syndrome) used to be considered as a kind of sub-case or extreme case of ADHD-I. However, this view is outdated. SCT is a disorder in its own right and occurs in around 50% of people with and without comorbid ADHD.
In the presence of ADHD comorbidity, SCT appears to occur as frequently in ADHD-HI sufferers as in ADHD-I sufferers.
SCT was renamed CDS in 2022.
We consider the term “slowed thinking” to be inaccurate and inappropriate in relation to SCT. We rather perceive a slowed down decision making. The ability to think quickly is basically given; we suspect - as an unverified hypothesis - an overabundant blockade of the PFC by noradrenaline and possibly other neurotransmitters via the alpha-1-adrenoceptor.
1. Symptoms of SCT
In the following list of SCT symptoms, the numbers indicate how often the respective symptom occurs in SCT according to Becker et al.. Lee et al. also name several of the symptoms as typical for SCT:
- Quickly tired or exhausted 1.02
- Low activity level, hypoactivity 0.97
- Stares into space 0.96
- Dozy, sleepy, yawns (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 train of thought 0.86
- Slow thinking 0.82
- Quickly gets confused 0.85
- Lost in thought 0.81
- Mental switch off 0.82
- Difficulty expressing thoughts 0.78
- Often considerable difficulty in making decisions (sluggish - in our experience)
- Social seclusion
A comprehensive review article found 13 distinct symptoms for SCT that are distinguishable from ADHD, but not distinct enough to be used diagnostically.
One study found the Adult Concentration Inventory (ACI) to be appropriate for diagnosing SCT. SCT was clearly associated with
- Stronger internalizing symptoms
- Time management and self-organization difficulties
- Poorer sleep quality
- Shorter sleep duration
- Lower sleep efficiency
- More daytime sleepiness.
SCT is not synonymous with reduced cognitive performance. There are highly gifted SCT sufferers. This is consistent with the finding that SCT does not correlate with slow processing speed.
The slowed cognitive performance specific to the Sluggish/Underarousal subtype does not mean that intelligence would be reduced to the same degree. What is meant by this is that SCT is not the mere result of reduced intelligence. We know several individuals whom we perceive as SCT who have PhDs or are otherwise highly intelligent or even highly gifted. Rather, it appears that decision-making processes are slowed or impeded. Conversely, high IQ might mitigate SCT symptomatology.
The ADxS.org online SCT test (as of September 2022) clearly showed a negative correlation of SCT symptoms with the reported highest IQ test score.
||SCT symptoms (out of 26)
|150 and higher
|140 - 149
|130 - 139
|120 - 129
|110 - 119
|100 - 109
|90 - 99
|80 - 89
A total of 78 (out of 381) subjects with IQs of 120 and above had 20 SCT symptoms and above (out of 26).
Of a total of 2039 subjects, only the 1640 subjects who reported not having ADHD or based your data on how they are when 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 them less frequently. The values in the two IQ groups below 100 should be viewed with caution due to the low number of subjects.
Overall results are limited by the fact that subjects participated in the SCT online test linked to ADxS.org out of their own interest.
The massive overrepresentation of high IQ scores is likely to stem from a 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
Thus, the term sluggish cognitive tempo does not really seem appropriate. Barkley also disagrees with the SCT designation. SCT was renamed CDS (Cognitive Disengagement Syndrome) in 2022. In our view, Sluggish Decisioning Might be more appropriate.
In our impression, SCT sufferers fail particularly frequently as self-employed persons.
2. SCT (Sluggish Cognitive Tempo) as a disorder in its own right
SCT was previously described as an extreme expression of ADHD-I subtype or ADHD-I-like type with slowed cognitive performance.
A growing body of research, meanwhile, is concluding that SCT is a distinct and distinguishable disorder from ADHD. Strong distinctiveness from ADHD-I has been found for 13 of the 15 SCT symptoms.
2 Studies found evidence that SCT could be considered a group of symptoms that occurs in various mental disorders. When ADHD, depression, anxiety disorder, sleep disorders, and alcohol and cannabis abuse were taken out, less than 5% of subjects remained who had high SCT scores.
A metastudy 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.
A large study of over 2,000 families found that among children, only 48% of SCT sufferers also had ADHD and only 35% of ADHD-HI sufferers also had SCT. Those with SCT without ADHD had higher levels of anxiety, depression, shyness, and sleep disturbances than those with ADHD without SCT. ADHD without SCT, on the other hand, had greater executive function deficits and more frequent ODD than those with SCT. SCT and ADHD did not differ in terms of friendships and social or academic impairments.
However, SCT and ADHD appear to have significant comorbidity. One report suggests that 30% to 63% of ADHD-I sufferers also have significant SCT symptoms.
Barkley had already advocated in the early 2010s that SCT was a separate disorder, which has since been proven true. Meanwhile, in the early 2000s, he had similarly advocated that ADHD-I was a separate disorder from ADHD-HI, which has not proven to be true.
Results to date from the ADxS.org online questionnaire on SCT (as of September 2022) also indicate that SCT, while highly correlated with ADHD overall, is largely independent of 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 were nearly identical (ADHD-HI / ADHD-C: 15.4; ADHD-I: 16.9 of 26 possible SCT symptoms when judged as they are when not taking ADHD medication). If ADHD-HI subjects assessed themselves as they are when taking ADHD medication, ADHD-HI subjects had 13.5 symptoms (n = 52, minus 12.3%), whereas ADHD-I subjects had 15.4 symptoms (n = 62, minus 8.9%). This suggests that ADHD medication may also have some positive impact on SCT symptoms and that this may be greater in ADHD hyperactivity sufferers.
In contrast, the n = 33 participants who indicated they certainly did not have ADHD or SCT achieved a mean SCT score of 12.5. To date, no participant indicated they certainly had SCT and not ADHD. This is not surprising due to the unfamiliarity of the disorder.
Men averaged 15.7 symptoms (n = 713), and women averaged 15.4 symptoms (n = 1,250) out of 26 possible symptoms.
Recent research indicates that SCT should differ from ADHD-I in the following ways:
SCT appears to correlate significantly more often than ADHD-I with
- Later withdrawal from addictive substances
- In contrast, one study found no correlation between SCT and anxiety symptoms.
- Increased BIS
- Increased BAS fun-seeking
SCT appears to be even more strongly associated with later internalizing behavior than ADHD-I.
SCT is reported to correlate (differently or more strongly than ADHD-I) with later shyness or internalizing symptoms and lower extraversion.
- Whereas externalizing symptoms were associated with hyperactivity/impulsivity symptoms of ADHD-HI in one study, internalizing symptoms were significantly correlated with SCT in ADHD-affected children and adolescents. Although social withdrawal was statistically significantly correlated with ADHD-I and inattention (compared with ADHD-HI), this relationship was mediated by SCT severity.
SCT, like ADHD-I, is reported to correlate with later social difficulties, but other studies do not confirm this.
SCT shows even greater social withdrawal than ADHD, according to one study, which another study only partially confirms.
ADHD-I correlated with later poorer math performance and slower processing speed, whereas SCT more consistently predicted later poorer reading performance.
SCT correlated (unlike other ADHD symptoms) with suicidal tendencies, which in turn correlated with depression.
SCT showed lower memory performance than ADHD-I and non-affected.
- Motor speed and reaction times
SCT showed not quite as reduced psychomotor speed and better neurocognitive index compared with ADHD-I.
SCT showed faster reaction times than ADHD-I.
- Slower psychomotor speed and longer reaction times correlated with levels of inattention.
- In contrast to ADHD, the variance in reaction time is not increased in SCT
- The unimpaired variance in reaction times at least tends to be consistent with a report that SCT had lower impairments in executive functions (mediated, like reaction time variance, by working memory) than ADHD.
SCT, unlike ADHD, is said to
- Occur equally often in men and women
- Occur just as frequently in adults as in children and adolescents, even if its onset is somewhat later than ADHD. So there is no partial disappearance of symptoms in a subset of sufferers.
- In contrast, a 7-year longitudinal study of 639 twins found that SCT was usually short-lived (1 - 2 years) and had no lasting detrimental effect on academic achievement.
SCT showed abnormalities in HRV compared with ADHD, which could indicate problems with arousal.
SCT showed decreased conscientiousness.
SCT sufferers who also have ADHD are said to be particularly frequent MPH nonresponders. In particular, elevated SCT Sluggish / Sleepy factor scores are said to indicate MPH nonresponding. In contrast, neither elevated SCT Daydreamy symptoms nor ADHD subtype (ADHD-HI or ADHD-I) differed in MPH responding rates (arguing against the this-side hypothesis of SCT as a subtype of ADHD-I).
SCT, like ADHD, begins in early childhood, although in SCT symptoms increased moderately after age 5, whereas inattention remained more constant. SCT was subsequently distinguishable from ADHD, although highly correlative. Lower parental education correlated with higher SCT ratings by teachers. African Americans had higher inattention and lower teacher SCT ratings.
- Unlike ADHD-I, SCT is not said to have features of emotional dysregulation.
- In a large study, SCT symptoms correlated with more frequent
- Mind wandering
The study further found the first 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 reference to time representation, repetition of non-words, and remembering sentences’unremarkable. Instead, SCT seems to be more closely associated with features of a social (pragmatic) communication disorder.
3. Neurophysiological characteristics of SCT
- The specific SCT symptoms (sluggish, underarousal) could be caused by a noticeable deficit in the uptake of dopamine and norepinephrine.
SCT is thought to correlate with inactivity in the superior parietal lobe (SPL).
- Sluggish Cognitive Tempo is said to correlate with attention problems, but not hyperactivity or aggression problems. Likewise, sleep problems are said to be less frequent.
- Sluggish cognitive tempo - unlike ADHD - is not conspicuous in the frontal and frontocentral theta-beta ratios of the EEG, he said.
SCT correlates with impaired information processing capacity and slowed (visual) information processing speed, according to one study.
Another study found no correlation of SCT with decreased information processing speed, but a correlation with decreased working memory speed as well as increased inhibition speed. Therefore, a combination of slowed working memory and accelerated inhibition was suspected.
- A high load on working memory significantly impairs information processing speed. Nevertheless, in ADHD, manipulations of working memory were found to impair Information Processing Speed as little as vice versa. This suggests that working memory impairments and information processing speed impairments in ADHD are caused by different brain functional areas.
- One interesting report cites partial sleep of the brain as a possible cause of some SCT symptoms or mind wandering.
- Adolescents with SCT completed the Wechsler Symbol Search and Coding subtests and the Grooved Pegboard Test. Their parents reported no symptoms involving symbol search or coding scores about the affected individuals, whereas the affected individuals themselves reported significantly decreased coding scores. Parents and sufferers alike consistently reported symptoms that significantly correlated with slower Grooved Pegboard time. The hypothesis from this is that SCT correlates more clearly with performance on the processing speed task as motor demands increase.
- A study of children with ADHD 8 to 12 years of age 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, stronger 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 reactivityand greater BIS activation.
4. Medication for SCT
- In one study, atomoxetine significantly improved 7 of 9 Kiddie-Sluggish Cognitive Tempo Interview (K-SCT) symptoms in SCT. Symptom improvement in SCT was completely independent of ADHD symptoms. This also suggests that SCT is an independent disorder or has an independent disorder cause and can coexist with ADHD.
SCT sufferers are particularly likely to be MPH nonresponders, according to one study; in contrast, ADHD-HI and ADHD-I did not differ in MPH response rates in this study, which is controversial.
- One study found improvement in SCT symptoms with MPH only in relation to the school environment. Daydreaming and oppositional behavior correlated with lower MPH response in SCT.
- Results from the ADxS.org SCT online test suggest that ADHD medications may provide some improvement in SCT symptoms (see above).