Neurocognitive effects of methylphenidate in adults with attention-deficit/hyperactivity disorder: A meta-analysis.

PIEVSKY, M. A., and R. E. McGrath. Neurocognitive effects of methylphenidate in adults with attention-deficit/hyperactivity disorder: A meta-analysis…NEUROSCI BIOBEHAV REV 81(1) XXX-XXX, 2017.- This meta-analysis summarized 21 double-blind randomized controlled trials with a mean study duration of 18 days comparing the neurocognitive functioning of adults with attention-deficit/hyperactivity disorder (ADHD) on methylphenidate vs placebo. Effect sizes were weighted using a random-effects model. Scores on neurocognitive measures and tests of driving ability were on average higher on methylphenidate than on placebo, g = 0.17, p < .01, 95% CI = [0.05, 0.28], with little heterogeneity, Q(20) = 15.05, p = .77, I2 = 0. Performance on methylphenidate was significantly better than on placebo for the following domains: working memory (mean g = 0.13, 95% CI = [0.00, 0.26]), reaction time variability (0.16, [0.03, 0.28]), vigilance (0.22, [0.11, 0.33]), driving (0.22, [0.10, 0.34]), and response inhibition (0.23, [0.10, 0.36]). Quantitative and qualitative assessment revealed evidence of publication bias. Summarizing across studies, methylphenidate improved the performance of adults with ADHD on neurocognitive measures and tests of driving, suggesting that methylphenidate is an effective treatment for adults with ADHD and can improve processes related to attention and concentration.

The Neurocognitive Profile of Attention-Deficit/Hyperactivity Disorder: A Review of Meta-Analyses.

OBJECTIVE: Numerous meta-analyses have summarized studies comparing the neurocognitive performance of individuals with attention-deficit/hyperactivity disorder (ADHD) to that of healthy controls. METHOD: The present study is a systematic review and quantitative summary of those meta-analyses that aimed to determine the extent to which individuals with ADHD differ cognitively from typically developing controls. RESULTS: Of 253 standardized mean differences (SMDs) drawn from 34 meta-analyses, 244 (96%) were positive, indicating better neurocognitive performance in the control group than the ADHD group. The mean effect size was .45 (SD = .27). Unweighted means of SMDs for neurocognitive domains ranged from .35 (set shifting) to .54 (working memory). When weighted by the number of studies aggregated, they ranged from .35 (set shifting) to .66 (reaction time variability). Neurocognitive domains with mean effects over .50 included working memory (.54), reaction time variability (.53), response inhibition (.52), intelligence/achievement (.51), and planning/organization (.51). When weighted by number of aggregated studies, the domains with mean effects over .50 were reaction time variability (.66), intelligence/achievement (.60), vigilance (.56), working memory (.54), and response inhibition (.52). Age moderated the relationship between ADHD diagnosis and neurocognitive functioning, with greater between-groups differences among children and adults than among adolescents. Funding also moderated this relationship: meta-analyses that received drug funding found larger effect sizes than those without drug funding. CONCLUSIONS: The evidence suggests that ADHD is associated with substantial deficits across a variety of neurocognitive domains. This is the most in-depth review of the neurocognitive functioning of people with ADHD to date.