Risk of schizophrenia in patients previously diagnosed with obsessive-compulsive disorder: a systematic review

This systematic review aimed to synthesize longitudinal evidence on the risk of developing schizophrenia (SCZ) among individuals previously diagnosed with obsessive-compulsive disorder (OCD).

A systematic search of longitudinal studies examining the temporal relationship between OCD and SCZ was conducted in PubMed, PsycINFO, Embase, and Scopus in September 2023 and subsequently updated in January 2026. We included original longitudinal observational studies reporting the incidence of schizophrenia in patients with a prior OCD diagnosis compared to controls. Cross-sectional designs, reviews, and studies lacking temporal delimitation were excluded. Two independent reviewers performed study selection, data extraction and risk of bias assessment using the ROBINS-E tool.

A total of 1,390 records were identified; 30 studies were screened in full, and 4 large national cohort studies (over 3 million subjects) met the inclusion criteria. Across all cohorts, individuals with OCD demonstrated a substantially increased risk of developing SCZ. Reported effect sizes included an Incidence Rate Ratio (IRR) of 6.90 (95% CI, 6.25-7.60); Hazard Ratios (HR) of 30.29 (95% CI: 17.91 - 51.21) and 10.46 (95% CI, 6.07-18.00); and a Relative Risk (RR) of 2.7 (95% CI, 2.2-3.3). The highest risk estimates were observed within the first five years after the initial OCD diagnosis, particularly during the first two years. Limited evidence also suggested that parental OCD may increase the likelihood of SCZ in subsequent generations. Despite methodological heterogeneity and the limited number of studies, available longitudinal evidence consistently shows that individuals with OCD are at significantly elevated risk of later developing schizophrenia. These findings underscore the importance of long-term clinical monitoring and early detection of psychotic symptoms in this population. Study protocol is available in PROSPERO (CRD42023475499).