Probiotic supplement as an adjunctive therapy with Ritalin for treatment of attention-deficit hyperactivity disorder symptoms in children: a double-blind placebo-controlled randomized clinical trial

Purpose Accumulating evidence highlights the importance of microbiota-directed intervention in neuropsychiatric disorders. This study aims to investigate the effects of probiotic supplements as an adjunct therapy in combination with Ritalin in children with attention-deficit hyperactivity disorder (ADHD). Design/methodology/approach Children with ADHD, aged 6–12 years, who had an intelligent quotient of ≥70 were enrolled in the study. Participants were randomly assigned to either the group that received probiotics or the group that received the placebo in addition to the weight-adjusted dose of Ritalin. Parents were asked to complete the revised Conners Parent Rating Scale–short version (CPRS–RS), and the psychiatrist completed the seven-point Clinical Global Impression–Severity (CGI–S) scale. Two study groups were compared in three time points, including T1 (before intervention), T2 (at the end of fourth week) and T3 (at the end of the eighth week). Findings A total of 38 participants completed the study. After eight weeks of intervention, the probiotic group had a significant improvement regarding CPRS–RS scores in T2 (9.4 unit, p = 0.014) and T3 (18.6 unit, p < 0.001), compared to placebo. In addition, children in the probiotic group had 0.7 unit lower CGI in T3 ( p = 0.018) than the placebo group. A significant reduction of CGI scores was observed in each interval (T2 vs T1, T3 vs T2 and T3 vs T1; p < 0.05). This significant change in CGI score between intervals was also detected in the placebo group in T2 vs T1 ( p = 0.002) and T3 vs T1 ( p < 0.001). Mean CPRS scores of the groups were different in T2 and T3 ( p = 0.011 and p < 0.001, respectively) and mean CGI scores of the two study groups were different in T3 ( p = 0.018). Originality/value Eight weeks of supplementation with probiotics had a favorable effect on symptoms and severity of ADHD. Therefore, probiotics as an adjuvant treatment might have a promising efficacy regarding the management of ADHD.