Comorbidity of epilepsy and attention-deficit/hyperactivity disorder: a systematic review and meta-analysis

Epilepsy and attention-deficit/hyperactivity disorder (ADHD) are common neurological and neuropsychiatric disorders, respectively, that can exist as comorbidities. However, the degree of comorbidity between both disorders has never been quantified based on a systematic review with meta-analysis. We performed a systematic search of the literature in Embase, PubMed, PsychINFO and the Cochrane Library on June 20, 2022. In a meta-analysis of 63 studies with a total sample size of 1,073,188 individuals (172,206 with epilepsy and 900,982 with ADHD) from 17 countries, the pooled prevalence of ADHD in epilepsy was 22.3% (95% CI 20.3-24.4%). The highest pooled prevalence was 12.7% (95% CI 9-17.1%) for ADHD-I subtype, whereas the pooled prevalence of epilepsy in ADHD was 3.4% (95% CI 2.53-4.21%). However, substantial heterogeneity in comorbidity rates was observed and partially attributed to the following factors: sample size, sample specification, geographical variations and diagnostic methods. Our study highlights the need for increased awareness of this diagnostic co-occurrence, and research is warranted to elucidate the underlying pathophysiological mechanisms.