[Bipolar disorder: a multifactorial disease].

Bipolar disorder is a multifactorial disease with a strong genetic component. However, environmental factors also play a role in the onset of the disease and in manic and depressive recurrence. The onset of the disorder is the consequence of a complex interaction between genetic and environmental factors. This gene-environment interaction is well illustrated by the influence of childhood trauma on the clinical expression of the disease in terms of age of onset, comorbidity and suicide. The complexity and heterogeneity of bipolar disorder require the identification of homogenous sub-groups with the use of biomarkers that could help reduce the etiological heterogeneity and better target the therapeutical options.