Diagnostic progression to schizophrenia in 35,255 patients with obsessive–compulsive disorder: a longitudinal follow-up study

Evidence suggests a continuity between obsessive–compulsive disorder (OCD) and schizophrenia. However, the factors that may predict diagnostic progression from OCD to schizophrenia remain unclear. A total of 35,255 adolescents and adults with OCD (ICD-9-CM code: 300.3) were enrolled between 2001 and 2010 and followed up at the end of 2011 for the identification of de novo schizophrenia (ICD-9-CM code: 295). The Kaplan–Meier method was used to estimate incidence rates, and the Cox regression was used to determine the significance of candidate predictors. At the end of the 11-year follow-up period, the crude cumulative progression rate from OCD to schizophrenia was 6%, and the estimated progression rate totaled 7.80%. Male sex (hazard ratio: 1.23), obesity (1.77), autism spectrum disorder (1.69), bipolar disorder (1.69), posttraumatic stress disorder (1.65), cluster A personality disorder (2.50), and a family history of schizophrenia (2.57) also were related to an elevated likelihood of subsequent progression to schizophrenia in patients with OCD. Further study is necessary to elucidate the exact pathomechanisms underlying diagnostic progression to schizophrenia in patients with OCD.