The effect of methylphenidate treatment on suspiciousness in children with ADHD alone or comorbid with ODD.

Objective: To assess the level of the suspiciousness in children with attention deficit/hyperactivity disorder (ADHD) and comorbid oppositional defiant disorder (ODD) in comparison to ADHD alone and the response of suspiciousness symptoms to methylphenidate (MPH) treatment.

Methods: In this open-label comparative study, children with DSM-IV-TR ADHD, aged 8-18 years, with (N = 30) or without (N = 30) ODD received MPH treatment for 12 weeks. The severity of ODD symptoms was assessed by the Kiddie-Schedule for Affective Disorders and Schizophrenia. The severity of ADHD symptoms was assessed by the ADHD-Rating-Scale-IV and suspiciousness was assessed at baseline and at endpoint by a scale designed especially for assessment of suspiciousness and named Suspiciousness Rating Scale (SRS).

Results: Significant reductions in SRS scores were detected in both groups following MPH treatment (before and after: p = .0012 and p = .0273, respectively). Only in the ADHD/ODD group a significant correlation was found between the rate of improvement in ADHD, as assessed by the ADHD-RS, and the reduction in suspiciousness, as assessed by the SRS (Spearman r = 0.48, p =  .0066).

Conclusions: In addition to the beneficial effect of MPH treatment on ADHD and ODD symptoms it also diminishes suspiciousness. However, due to the small sample size further studies are needed to confirm the present results.