Olfactory Dysfunction in Neurodevelopmental Disorders: A Meta-analytic Review of Autism Spectrum Disorders, Attention Deficit/Hyperactivity Disorder and Obsessive-Compulsive Disorder.

The meta-analysis included studies using different performance measures of olfactory function, which may reduce the precision of the synthesis. Many included studies recruited participants from outpatient clinics rather than community samples, potentially inflating the observed effect sizes. There were few effect sizes available for ADHD and for specific domains like odor intensity and hedonics, making these findings tentative. Moderator analyses relied on studies that reported relevant data (e.g., IQ, medication status), which was not available for all included studies. Publication bias was detected in the ADHD and OCD subgroups (significant Egger tests), though trim-and-fill adjustments were applied.

Do not conclude that ADHD is unrelated to olfactory dysfunction. While the primary analysis showed no significant deficit (d = -0.12), the authors detected publication bias and, after adjusting for it, found a moderate effect size (d = -0.40) that approached significance.