ADHD symptoms in relation to internalizing and externalizing symptoms in children: the mediating role of sluggish cognitive tempo

Objective: Although internalizing and externalizing disorders have received considerable attention among young population, the mechanisms that explain the relationships of internalization and externalization symptoms with attention deficit/hyperactivity disorder (ADHD) in children and adolescents are not well understood. Since sluggish cognitive tempo (SCT) symptoms had significant associations with ADHD, and internalization/externalization disorders, we examined whether SCT may mediate between ADHD symptoms and internalizing/externalizing problems during childhood. Methods: We performed a retrospective chart-review of 95 children and adolescents (76 boys and 19 girls, aged 6-16) with ADHD. The severity of ADHD was evaluated by Turgay DSM-IV-Based Disruptive Behavioral Disorders Screening and Rating Scale (T-DSMIV-S) completed by teachers. Measures of SCT, internalisation and externalisation symptoms, social, thought, and attentional problems were based on the Teacher Report Form (TRF) that was completed by subjects' primary teachers. Results: The withdrawn scores were significantly correlated with SCT scores, social problems, and ADHD-inattention. There was an inverse correlation between withdrawn and ADHD-hyperactivity/impulsivity scores. The mediation test using bootstrapping method showed that the indirect coefficient for SCT was significant, after controlling of ADHD-inattention and social problems covariates, consistent with partial mediation. Conclusion: Our results may demonstrate that while externalization symptoms were associated with hyperactivity/impulsivity symptoms of ADHD, the internalization symptoms were significantly related to SCT in youngs with ADHD. Specifically, although social withdrawal was significantly related to ADHD-inattention, this relationship was mediated by the severity of SCT.