Sluggish Cognitive Tempo - Epidemiology

Epidemiology

Recent studies indicate that the symptoms of SCT in children form two dimensions: daydreamy-spacey and sluggish-lethargic, and that the former are more distinctive of the disorder from ADHD than the latter. This same pattern was recently found in the first study of adults with SCT by Barkley. Both of these studies indicated that SCT is probably not a subtype of ADHD but a distinct disorder from it. Yet it is one that overlaps with ADHD in 30-50% of cases of each disorder, suggesting a pattern of comorbidity between two related disorders rather than subtypes of the same disorder.

In many ways, those who have an SCT profile have some of the opposite symptoms of those with classic ADHD: instead of being hyperactive, extroverted, obtrusive, and risk takers, those with SCT are drifting, introspective and daydreamy, and feel as if "in the fog" (although in excited states, an SCT patient behaves very similarly to a traditional ADHD patient). Due to their drifting tendencies, those with SCT have trouble with memory retrieval. They also don't have the same risk factors and outcomes. A key behavioral characteristic of those with SCT symptoms is that they are more likely to appear 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, an intense craving for emotional and intellectual stimulation. Those with SCT symptoms show a qualitatively different kind of attention deficit that is more typical of a true information input-output problem, such as memory retrieval and active working memory, and display a wavering "up and down" mental pattern with extremely variable levels of intense thought, hyperactivity, and failing memory. Conversely, those with the other two subtypes of ADHD are characteristically excessively energetic and have no difficulty processing information.

Despite the apparent incompatibility between SCT and hyperactivity, and contrary to previous suggestions that SCT could distinguish a distinct group within the ADHD-PI type, Barkley's study found that SCT was comorbid with ADHD-C almost as often as with ADHD-PI.