The following limitations in our research are noted. First, paediatric samples were under-represented compared to adults, likely due to general limitations in the extant literature on childhood OCD and our selection criteria requiring a OCD sample size of ≥100. Second, comorbidity evaluation was not consistent across studies, with several comorbidities not commonly reported in paediatric OCD studies (e.g., bipolar disorder, OCRDs, eating disorders, PTSD, psychosis) and only one adult study recording comorbidity rates for ASD. Third, a more nuanced lifespan examination of comorbidities was not possible given the nature of included samples and a lack of studies representing the elderly population with OCD. Fourth, several studies did not explicitly state assessment of lifetime vs. current comorbidities. To maximise data utilisation from the studies we treated all studies unclear in this regard as reporting lifetime comorbidity rates. Fifth, we did not find enough no. of studies that reported medical/neurological comorbidities. Sixth, due to lack of clarity on their use of standardised assessments, several large samples (e.g., registry based datasets), were not represented. Seventh, we could include only clinic-based studies for meta-analysis,
