Boys Score Higher Everywhere? Gender Differences in Parent-Reported ADHD Symptoms Across Age Groups and Four Countries.

Research suggests gender differences in parent-reported ADHD symptoms, but it remains unclear whether these differences vary across age group and countries. This study examined cross-national gender differences from early, middle and late childhood. Using a meta-analytic approach based on mean values, standardization data from the Strengths and Difficulties Questionnaire (Subscale Hyperactivity/Inattention) from England, the Netherlands, the USA, and Japan were aggregated. A mixed-effects meta-regression model was used to average gender differences and potential moderation by age group and the Gender Inequality Index (GII) simultaneously. The gender difference was significant overall (standardized mean differences [SMD] ≈ 0.27) and in all age groups (SMD early childhood ≈ 0.27, SMD middle childhood ≈ 0.36, SMD late childhood/adolescence ≈ 0.35). The GII did not explain the observed variability but was limited in variance. Residual heterogeneity suggests the involvement of additional factors. Results indicate that gender differences are existing in all age groups and countries. Limitations include the use of aggregated data, categorical age groups, and a small number of countries.