The symptoms of Sluggish Cognitive Tempo, under arousal, mental fogginess, under activity, and inattention are seen in about 30% to 50% of people with the Inattentive subtype of ADHD. It appears that SCT will earn a place in the soon to be published psychiatric diagnostic manual, the DSM-V. The appearance of SCT in the DSM-V will enable researchers to study people with these types of symptoms more carefully. This is important as very little is known about SCT.
While it is clear that not everybody with the Inattentive subtype of ADHD (ADHD-PI) has SCT, it is unclear if Inattentive ADHD will be separated from the combined type of ADHD (ADHD-C) and Hyperactive/Impulsive type of ADHD (ADHD-HI) in the DSM-V.
Some researchers have speculated that the diagnosis of Sluggish Cognitive Tempo (SCT) is simply the presentation of Inattentive ADHD in a person who is also depressed. Other researchers have proposed that anxiety can present as under arousal and can look like the symptoms of SCT.
A study performed at the University of Alabama at Birmingham by researchers Annie Garner MA, Sylvie Mrug, and Bart Hodgens Ph.D. set out to answer the question of the relationship between SCT and depression and anxiety. The researchers looked at seventy-three children with SCT and administered questionnaires to both the children and their parents inquiring about symptoms of depression and anxiety.
What the researcher found was interesting. They found that there was not relationship between reported anxiety and SCT and no relationship between reported depression and SCT in kids diagnosed with Sluggish Cognitive Tempo. The researchers did find that parents of kids diagnosed with SCT were more likely to report that their children were depressed but not that they were anxious. The researchers were unsure if this was because kids with SCT tend to 'look' depressed or if this was because parents were more aware and knowledgeable of the symptoms of depression.
I have heard of SCT referred to as a disorder that children 'outgrow'. In this context it is a developmental disorder tied to an immaturity of the part of the brain that manages motor and mental arousal levels. Using this model, the Hyperactive/Impulsive ADHD child would be at one end of the spectrum and the Sluggish Cognitive Tempo person would be at the other end of the spectrum.
SCT have been referred to as a mood disorder tied to the internalizing behaviors of anxiety and depression often seen in people with Inattentive ADHD. We have discussed this model above. Using this model, the symptoms of "sluggishness" would improve in people diagnosed with SCT if their anxiety and depression was treated.
The third model of SCT is a model that involves a problem with the part of the part of the brain that manages stores, organizes and retrieves information. These activities are called the executive functions of the brain. In general, the executive functions orchestrate numerous aspects of thought, memory, learning, emotion, arousal and action. When SCT is thought of as a problem of executive brain function it fits much more concretely in the ADHD camp.
It is important to determine whether the symptoms of Sluggish Cognitive Tempo are the result of an Executive Function problem as opposed to a problem with immaturity or a problem with a mood disorder as properly treating these symptoms depend on these determinations.