Thirty sham-controlled trials challenge claims about brain stimulation and cognition

A device can change neural activity without improving the thinking and daily functioning we care about. In neurodevelopmental conditions, noninvasive stimulation has attracted attention because it seems able to influence brain networks directly.

This meta-analysis pooled sham-controlled trials and treated multiple related outcomes as statistically dependent, an important methodological safeguard. Despite the number of tested cognitive domains, no specific domain showed a dependable gain over sham. That does not mean individualized future protocols cannot work; it means the currently heterogeneous approaches have not earned a broad therapeutic claim.

The evidence: 30 randomized trials across autism, ADHD and intellectual disability; 178 effects spanning seven cognitive domains, modeled with dependence-aware multilevel methods. No individual cognitive domain showed a statistically reliable advantage over sham. For working memory, Hedges g -0.16 (95% CI -0.37 to 0.05); for cognitive flexibility g -0.12 (-0.38 to 0.13). The small cross-domain pooled estimate g -0.18 (P=0.035) had a wide 95% prediction interval (-1.01 to 0.66) and no robust domain-specific signal.

enhancer for neurodevelopmental disorders.