March 17, 2022
A Chinese study team performed a systematic search of peer-reviewed journal literature to identify randomized controlled trials (RCTs) examining the efficacy of cognitive training as a treatment for youths with ADHD.
Seventeen RCTs with a combined total of 1,075 participants met standards for inclusion in a series of meta-analyses. Seven RCTs used waitlist controls, seven used placebo training, two used treatment-as-usual, and one used active knowledge training. Participants were unmediated in four RCTs, with varying proportions of medicated participants in the remaining thirteen.
A meta-analysis of 15 RCTs, with a combined 789 participants, assessed changes in inattention symptoms following treatment, as rated by parents or clinicians. It found a small-to-medium effect size improvement in symptoms of inattention. There was no indication of publication bias, but between-study heterogeneity was very high.
But that gain vanished altogether when combining only the six RCTs that were blinded, meaning the symptom evaluators had no idea which participants had received cognitive treatment and which participants had not. There was zero difference between the treatment and control groups. Significantly, between-study heterogeneity also diminished markedly, becoming low to moderate.
A second meta-analysis, of 15 RCTs with a combined 723 participants, assessed changes in hyperactivity/impulsivity symptoms following treatment, as rated by parents or clinicians. It found no significant difference between participants who received cognitive training and controls. There was no sign of publication bias, and between-study heterogeneity was moderate-to-high.
The three remaining meta-analyses looked for improvements in executive functions, using the Behavior Rating Inventory of Executive Function (BRIEF).
A meta-analysis of 13 RCTs, with a combined 748 participants, found a small-to-medium effect size improvement in the global executive composite index of BRIEF, as evaluated by parents. There was no sign of publication bias, and between-study heterogeneity was moderate-to-high.
But that improvement again disappeared altogether when considering only the five RCTs that were blinded. Between-study heterogeneity also became insignificant.
A meta-analysis of 6 RCTs with 401 participants found no significant improvement in the behavioral regulation index of BRIEF. Heterogeneity was negligible.
Finally, a meta-analysis of 7 RCTs with 463 participants also found no significant improvement in the metacognition index of BRIEF. In this case, between-study heterogeneity was high.
While acknowledging that "when analyses were set in blinded measures, effect sizes were not statistically significant," the author nevertheless concluded, "In summary, multiple cognitive training alleviates the presentation of inattention and improves general executive function behaviors in children with ADHD." This suggests an underlying bias on the part of the study team in favor of treatment even when not supported by best (i.e., blinded) methodological practices.
Shuxian Chen, Jinglong Yu, QiangZhang, Jin Zhang, Ying Zhang, and Junhong Wang, "Which Factor Is More Relevant to the Effectiveness of the Cognitive Intervention? A Meta-Analysis of Randomized Controlled Trials of Cognitive Training on Symptoms and ExecutiveFunction Behaviors of Children With Attention Deficit Hyperactivity Disorder,". Frontiersin Psychology (2022)published online,https://doi.org/10.3389/fpsyg.2021.810298.