Obsessive compulsive disorder prevalence increases with latitude

Many individuals with obsessive compulsive disorder (OCD) report difficulty falling asleep until later than desired. This may reflect a misalignment between the sleep-wake cycle and the natural light dark cycle. Delayed bedtimes are related to disruptions in cognitive processes, increases in repetitive negative thinking, and OCD symptoms. Misalignment is more common in higher latitudes. AIMS: We hypothesized that the prevalence of OCD would be positively correlated with latitude. A systematic review of the literature identified peer-reviewed publications with estimates of OCD prevalence in the general population. Twenty-four estimates of the lifetime prevalence of OCD were identified and showed that the prevalence of OCD was significantly positively correlated with latitude. Other potential alternative individual, community and study specific factors were not significantly correlated with OCD prevalence. Finally, parallel analyses of a “psychiatric control” (panic disorder) failed to find a significant relationship between panic disorder and latitude. Findings from this study support a relation between latitude and OCD and suggest potential specificity of the relation to OCD vs factors related to mental health concerns broadly. These findings are consistent with recent results suggesting that the timing of sleep may be important in OCD. Future work in this area is warranted.