Researchers pooled results from fifteen trials, reported in 16 papers, covering 759 children with ADHD aged 3 to 18 years, drawn from 695 nonduplicate records. All were randomized controlled trials of cognitive training.
Training clearly helped working memory. Children did better on verbal memory tasks, a moderate effect (SMD 0.52). They also improved on visual memory tasks (SMD 0.47). Parents reported better everyday planning and self-control (SMD 0.35).
The effect on ADHD symptoms depended on who rated the children. When raters were close to the child and likely knew about the treatment, the effect on overall symptoms looked moderate (SMD 0.37). When raters were probably blinded, that effect shrank by about half (SMD 0.20). Inattention followed the same pattern and, under blinded raters, was no longer clearly above zero (SMD 0.32). Hyperactivity and impulsivity did not improve. Academic performance did not improve either.
Training that targeted several thinking skills at once showed the largest symptom effect, but only on ratings that were not blinded (SMD 0.79). The authors noted limits. Only 5 of the trials used intention-to-treat analysis, the results varied a lot between studies, and the blinding labels were uncertain.
Source: Samuele Cortese, Maite Ferrín, Daniel Brandeis, et al.. Cognitive Training for Attention-Deficit/Hyperactivity Disorder: Meta-Analysis of Clinical and Neuropsychological Outcomes From Randomized Controlled Trials. Journal of the American Academy of Child & Adolescent Psychiatry (2014). doi:10.1016/j.jaac.2014.12.010