Abstract
BACKGROUND: Although attention deficit hyperactivity disorder (ADHD) is known to be common in psychotic disorders, reported prevalence rates vary widely, with limited understanding of how different factors (eg, assessment methods, geographical region) may be associated with this variation. The aim was to conduct a systematic review and meta-analysis to determine the prevalence of ADHD in psychotic disorders and factors associated with the variability in reported rates. STUDY DESIGN: Searches were conducted in MEDLINE, Embase, PsycINFO, CINAHL, and Scopus in May 2023. Studies were eligible if the frequency of ADHD was reported in psychotic disorder samples. Pooled prevalence meta-analyses were performed. Subgroup analyses and meta-regressions explored whether demographic and study characteristics were associated with reported rates. STUDY RESULTS: Thirty-six studies were included, involving 30 726 individuals. The pooled lifetime prevalence of ADHD in psychotic disorders was 18.49% (95% CI 11.78%, 27.83%). The between-study heterogeneity was high (I2 = 98.4% [95% CI 98.2%, 98.6%]). Subgroup analyses revealed higher prevalence rates when using ADHD DSM-IV criteria compared to International Classification of Diseases (ICD)-10. Rates in childhood-onset psychotic disorders were higher than adolescent- and adult-onset psychotic disorder samples. Rates were higher in North America compared to other regions. Meta-regressions indicated a decrease in prevalence rates with publication year. CONCLUSIONS: The prevalence of ADHD in psychotic disorders appears higher than in the general population, highlighting the need for clinical attention and further research into this comorbidity. Reported rates, however, vary significantly. Reasons may include diagnostic criteria, age of psychosis onset, region, study design, and publication year. Future research should investigate these factors using rigorous ADHD assessment protocols.