Abstract
Little is known about the prevalence and stability of sluggish cognitive tempo (SCT) compared to other symptom clusters. Parent SCT ratings at baseline (mean age 9 years) and 8-years follow-up were compared with eight other symptom clusters (inattention, impulsivity, hyperactivity, oppositional behavior, irritability/temper outbursts, conduct problems, anxiety, and depression) in a population-based sample of 376 children. SCT was present in 7% of children at baseline and 9% at follow-up, with a nonsignificant difference between these prevalence rates and between mean SCT scores. However, the classification of individuals with and without SCT changed considerably; 63% of those with SCT at baseline remitted by follow-up and 71% with SCT at follow-up were new cases without SCT at baseline. Only 3% had SCT at both time points. Findings were similar for most other symptom clusters. For all nine clusters, symptom scores were not elevated at baseline and at follow-up for most children (82%-91%). The SCT prevalence rate at baseline and at follow-up did not differ significantly from prevalence rates for most other clusters. However, SCT was the only symptom cluster for which mean scores did not decrease significantly over time and SCT had a significantly higher rate of persistence than six of the eight other symptoms clusters. Analyses based on group data (mean SCT scores and prevalence rates) indicate high group stability, whereas individual data analyses (change in SCT classification over time) show substantial instability. Despite this, the finding that 37% of children continued to have SCT 8 years later is clinically significant.