What's new? The clinical epidemiology of bipolar I disorder

The last few decades have seen a rapid change in our understanding of the epidemiology of bipolar disorder, which has only recently started to achieve major research attention. This article reviews recent developments. In addition to electronic searches using MEDLINE and PsycLIT, references from articles were identified, major journals hand searched, and major textbooks of psychiatry and epidemiology reviewed. Studies may have overestimated the prevalence of mania, and underestimated incidence. The incidence of mania may be increasing in recent generations, but the data remain inconclusive. Age at onset of mania is earlier than previously believed, and there are gender differences in epidemiology and clinical course. Ethnic differences in epidemiology and clinical course of bipolar disorder are highlighted. Comorbid alcohol and substance abuse are common in patients suffering from bipolar disorder and are associated with a more severe clinical course and a worse outcome. Urban living and lower socioeconomic and single marital status may be risk factors for developing bipolar disorder.