Introduction: Obsessive-compulsive disorder (OCD) is a chronic neuropsychiatric disorder that often begins early in childhood. Patients with OCD are known to seek help late after disorder onset, and therefore have a long duration of untreated illness (DUI), which is found to correlate with negative clinical outcomes. No meta-analysis has previously investigated this issue. Methods: Our protocol was pre-registered with PROSPERO (CRD42020165226). We followed PRISMA-guidelines and searched for relevant articles in four electronic databases. Meta-analyses of means based on random-effects (Der-Simonian-and-Laird-method) were used to derive the pooled estimates. Subgroup-analyses and meta-regressions were conducted to explore possible factors affecting help-seeking and DUI. Results: We included N = 31 studies in the quantitative synthesis, with 16 studies proving data for age at help-seeking and 16 studies providing data for duration of untreated illness. The pooled mean age at help-seeking was 28.66 years (95 % CI: 27.34–29.98), while the pooled mean interval between age at disorder onset and help-seeking was 6.97 (95 % CI: 5.69–8.24), and the pooled mean duration of untreated illness was 80.23 months (68.72–91.75), around 6.69 years, all with p < 0.001. Specific OCD-related factors affected help-seeking and duration of untreated illness. Conclusions: Patients with OCD seek for help late in the course of the disorder and have a long duration of untreated illness, which is associated with more negative prognosis. This meta-analysis confirms the long duration of untreated illness in OCD and proposes possible factors associated with the length of the help-seeking process and DUI.
