Autism Spectrum Disorder in Nigeria: A Systematic Review and Meta-analysis of Prevalence and Clinical Characteristics

Background Autism Spectrum Disorder (ASD) is a neurodevelopmental disorder with a significant global health burden, but epidemiologic data from low- and middle-income countries are limited. Evidence in Nigeria is fragmented, largely clinic-based, and has not been previously reviewed systematically. This review sought to provide an estimate of the prevalence of ASD in various Nigerian communities and to highlight common demographic and clinical features. Methods A PRISMA 2020 compliant systematic review with meta-analysis was performed. PubMed, Google Scholar, and grey literature were searched from inception to December 2025. We included studies that reported the prevalence or percentages of ASD among children (0–18 years) in Nigeria, using established diagnostic criteria or validated screening instruments. RoB was evaluated with the JBI tool for prevalence studies. Studies that reported similar clinic-based denominators were included in a random-effects meta-analysis; other studies were narratively synthesized. Results Eight studies were included following qualification for the criteria of inclusion. Three clinic-based neurology/psychiatry studies (n=5,393) yielded a clinic-based ASD pooled prevalence of 1.79% (95% CI: 1.29–2.47%; I²=60%). Adding one study from a private clinic with a limited neurological denominator raised the pooled estimate to 3.48%, but resulted in extremely high heterogeneity (I²=98.6%) and was therefore considered in the sensitivity analysis only. A single school-based study reported a prevalence of 2.9%, whereas screened high-risk and special-population samples showed significantly higher proportions (11–34%). Delay in diagnosis, male predominance, and frequent neurological comorbidities were consistent findings. The overall risk of bias was low to high, predominantly due to sampling limitations and methodological diagnosis variability. Conclusion Estimates of ASD prevalence for Nigeria differ greatly by setting, with evidence largely driven by clinic-based studies and marked by significant diagnostic delay. Accurate, population-based studies using a standardized two-stage ascertainment format are urgently required to guide early detection methods and national child health policy.