Sex/Gender Differences in Internalizing Problems of Autistic Children and Young People: A Systematic Review and Meta-Analysis

OBJECTIVE: Findings on the presence and direction of a sex/gender difference in internalizing problems for autistic children and young people (CYP) are inconsistent. This systematic review investigated whether autistic boys and girls differ in internalizing problem severity. METHOD: Studies comparing internalizing problems (including depression and anxiety) in autistic boys and girls using validated, continuous measures were included. Medline, Embase, PsycINFO, ASSIA, and Web of Science databases were searched. The Joanna Briggs Institute appraisal checklist for cross-sectional studies was used to assess risk of bias. Random-effects meta-analyses estimated effect size differences for overall internalizing, anxiety symptoms, and depression symptoms between autistic boys and girls. Moderation effects of age, IQ, and study methodology were examined through meta-regression. RESULTS: From 4,093 nonduplicate records, 56 studies were identified (autistic CYP: N = 13,410; girls: n = 3,657; boys: n = 9,753). Autistic girls experienced more anxiety symptoms than boys (Hedges' g = 0.14, 95% CI 0.04, 0.25, p = .010). This effect was larger in community (vs clinic) samples (β = .22, p = .027) and in samples with higher average age (β = .039, p = .010) and IQ (β = .015, p = .001). Autistic girls also showed higher overall internalizing (Hedges' g = 0.10, 95% CI -0.04, 0.23, p = .148) and depression (Hedges' g = 0.12, 95% CI -0.01, 0.25, p = .067) symptoms, but these differences did not reach significance. Heterogeneity for all pooled sex/gender differences was high. CONCLUSION: In autistic CYP, girls show more anxiety symptoms than boys, and this is most pronounced in older girls and those with higher IQ. This systematic review did not find strong evidence for sex/gender differences in overall internalizing problems or depression symptoms. However, the high heterogeneity cautions against drawing conclusions with certainty. PLAIN LANGUAGE SUMMARY: It is well established that autistic children and young people experience more internalizing problems than non-autistic youth, but studies have conflicting conclusions about sex/gender differences. This meta-analysis reviewed findings from 56 studies (N = 13,410, median age 10 years) to compare internalizing problems (like anxiety and depression) between autistic boys and girls. Results showed that autistic girls experienced slightly more anxiety symptoms than boys, especially if they were older or had higher IQ, but there were no statistically significant sex/gender differences for overall internalizing or depression symptoms. Differences varied widely between studies, so results should be viewed with caution. STUDY REGISTRATION INFORMATION: Systematic Review and Meta-analysis of Sex Differences in Internalising Problems of Autistic Children and Adolescents; https://www.crd.york.ac.uk/PROSPERO/view/CRD42023466929.