The incidence and prevalence of schizophrenia varies with latitude.

OBJECTIVE The aim of this study was to examine the association between latitude and the incidence and prevalence of schizophrenia based on two recently published systematic reviews. METHOD The analyses were based on 353 incidence rates (from 68 studies) and 258 prevalence estimates (from 94 studies). Exact latitude values were used for cities, and geocentroid values for other sites. Based on three equal latitude bands, we compared the frequency measures of schizophrenia for persons, males and females when adjusted for within-study variation. RESULTS Prevalence estimates from sites in the high-latitude band were significantly higher when compared with lower bands for persons, males and females. Incidence rates were positively associated with absolute latitude for males, but neither for females nor persons. CONCLUSION Variables that have latitude gradients warrant closer inspection in schizophrenia epidemiology.