Toward an understanding of bipolar disorder and its origin.

Bipolar disorder, a disease with significant morbidity and mortality, continues to present diagnostic and clinical challenges. Lifetime prevalence of bipolar I disorder has been estimated at 1.3%, with an equal distribution between males and females. Recognition of the illness may take years, but most patients are diagnosed before the age of 30. The role of genetic influences in bipolar disease is supported by family studies and high concordance rates among monozygotic twins. Current speculation proposes a likely interaction between genetic predisposition and environmental influences, including stressful life events. Diagnostic work-up should exclude mania secondary to drug use or general medical causes, particularly in patients whose symptoms begin after age 30 and in those with no family history of bipolar or unipolar disease. Patients with cyclothymia or thyroid dysfunction or postpartum women are at particular risk for bipolar disease. Substance abuse, which is extremely common among patients with bipolar disorder, interferes with diagnosis and can worsen the course of the disease. Alcohol dependence has been reported in approximately one third of those with bipolar I and one fifth of those with bipolar II disorder. To facilitate early diagnosis and effective management, clinicians should be aware of the risk factors, possible causes, and comorbidities of bipolar disease.