[Severe depression: genes and the environment]

Depressed patients with a familial history of depression are usually considered as more endogenous, with higher severity, therefore with a worst prognosis (regarding for example recurrence risk). The opposition between << neurotic-stress linked depression >> and << endogeneous-genetically related depression >> is being challenge in the present review. Indeed, differences in age at onset and selection bias are probably important confusing factors. The existence of an interaction between the involved vulnerability genes (G) and the triggering stressful events (E) was considered as providing meaningful insight for the respective parts of genetics and the environment. Although this approach is even more fragile regarding required sample sizes (larger) and the problem of false positive results (increased), the G*E approach is seducing as closer to reality, the onset of complex disorders being usually explained by those two risk factors.