Sluggish cognitive tempo

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Sluggish Cognitive Tempo (SCT) is a descriptive term which is used to better identify what appears to be a homogeneous group within the Predominantly Inattentive Type (ADHD/PI) DSM-IV classification. Those with SCT show a qualitatively different kind of attention deficit more typical of a true information input and output problem, than from those who have had a significant history of hyperactivity-impulsivity.^[1] SCT children show lower selective attention, sustained focus, and have memory retrieval problems more typical of a learning disability profile. They are also HYPO-active and are sluggish mentally and physically.

1 History of the term SCT and its relationship to the DSM
2 SCT is qualitatively different from classic ADHD
3 Treatment
4 Could SCT be an instance of childhood-onset dysexecutive syndrome?
5 See also
6 References
7 External links

[edit] History of the term SCT and its relationship to the DSM

Sluggishness, drowsiness, and daydreaming were the characteristics listed in the DSM111(1980-1987) that were to also be present in the diagnosis of Attention Deficit Disorder (ADD) without Hyperactivity. In a study looking at these symptoms(Lahey et al., 1988) the authors stated, "these symptoms were statistically extracted as a distinct factor", coined, Sluggish Cognitive Tempo. The Sluggish Tempo factor was found to correlate significantly to the Inattention factor, but only when Hyperactivity-Impulsivity symptoms were absent.

Sluggish Cognitive Tempo symptoms were removed from the Inattention symptom list in 1988 because of poor negative predictive power for the inattentive subgroup. The presence of these symptoms tended to predict Inattention but their absence did not predict the absence of Inattention. This analysis did not take into account the possibility that the SCT symptoms could help predict a distinct grouping within the ADHD/PI subgroup and that the ADHD/PI subgrouping could be heterogeneous in nature. ^[2]

In the DSM-IV with its new classification of symptoms for predominately inattentive ADHD, 50 to 70% of those with a ADHD/PI diagnosis have subclinical levels of hyperactivity-impulsiveness symptoms. ^[3] People with ADHD combined type (ADHD/C) and predominantly hyperactive–impulsive type (ADHD/PHI) may outgrow some, or most of their hyperactive symptoms during or after childhood, while inattentive symptoms typically remain into adulthood. In contrast, those with SCT have had only inattentive features from a young age with no, or very little history of hyperactivity-impulsiveness. Dr. Russell Barkley has proposed that the DSM4 designation of ADHD/PI be used only for those displaying purely inattentive symptoms and that those who who have had a history of any hyperactivity be designated as ADHD combined subtype. Currently, one can have a few hyperactive symptoms and still receive a diagnosis ADHD/PI. Others believe that SCT should be classified as a new separate disorder when the DSM is next updated. ^[4]

[edit] SCT is qualitatively different from classic ADHD

In many ways those who have an SCT profile have the opposite symptoms of those with classic ADHD. They also don't have the same risks and outcomes. Instead of being hyperactive, social, extroverted, and overly talkative, those with SCT are hypoactive, passive, and shy. Their demeanor is sluggish and they logically also process information more slowly. Conversly those with classic ADHD are more impatient, antsy, and have no difficulty processing information. A key behavioural characteristic of those with SCT characteristics is that they are more likely to be lacking motivation. They lack energy to deal with mundane tasks and will consequently seek things that are mentally stimulating because of their underaroused state. Conversely, those with the other two subtypes of ADHD are characteristically more impulsive, distracted, and have low goal persistence.

Selective attention difficulties of those with SCT manifests itself academically, in that they are prone to making more mistakes while working. Those with classic ADHD do not have this difficulty. Those with SCT have difficulty with verbal retrieval from long term memory, and also have greater visual spatial deficits. They have deficits in working memory which has been described as the ability to keep multiple things in mind for manipulation, while keeping this information free from internal distraction. Consequently, mental skills such as calculation, reading, and abstract reasoning are often more challenging for those with SCT. They also have a more disorganized thought process, a greater degree of sloppiness, and lose things more easily. They tend to have a greater degree of comorbid learning disabilities. Instead of having greater difficulty selecting and filtering sensory input as is in the case of SCT, people with ADHD/C and ADHD/PHI, have problems with inhibition.

Studies indicate that Comorbid psychiatric problems are more often of the internalizing variety with SCT, such as anxiety, depression, and social withdrawal. Their typical shy nature and slow response time has often been misinterpreted as aloofness or disinterest by others. In social group interactions those with SCT may be ignored. Those with the other types of ADHD are more likely to be rejected in social situations because of more intrusive or aggressive behaviour. Those with classic ADHD also show externalizing problems such as substance abuse, oppositional-defiant disorder, and, to a lesser degree, conduct disorder. ^[5] ^[6]

Finally a vast majority of those with classic ADHD clinically respond to stimulant medication with significant reductions in symptoms. Only a minority of those with an SCT profile respond clinically to stimulant medication.

[edit] Treatment

Those with SCT do not respond to methylphenidate (Ritalin) to anywhere near the same degree as do those with ADHD/C and ADHD/PHI. Roughly one in five responds with a therapeutic decrease in symptoms, while two thirds of this population will show mild benefits. It has been suggested that amphetamine (Adderall) has a greater success rate because unlike Methylphenidate, it also promotes the release of the neurotransmitters dopamine and norepinephrine which may induce a more aroused state. Those with SCT also generally respond better to smaller doses than do the other two subtypes of ADHD.

[edit] Could SCT be an instance of childhood-onset dysexecutive syndrome?

Adele Diamond has recently postulated that the core cognitive defitcit of SCT is working memory or as she postulated childhood-onset dysexecutive syndrome. She stated:

"Instructional methods that place heavy demands on working memory will disproportionately disadvantage individuals with ADD".
"language problems often co-occur with ADD, and it is suggested that part of the reason might be that linguistic tasks, especially verbal ones, tax working memory so heavily. Spatial and artistic skills, however, are often preserved or superior in individuals with ADD."
"The working memory deficit in many children with ADD is accompanied by markedly slowed reaction times, a characteristic that covaries with poorer working memory in general".
"Individuals with ADD have difficulty maintaining a sufficiently high level of motivation to complete a task...They go looking for something else to do or think about because they are bored...to remedy a general lower arousal level.."^[7]