La dépression sévère représente un enjeu majeur de santé publique. La physiopathologie de la maladie résulte de l’intrication de facteurs biologiques, d’apprentissages émotionnels et cognitifs et d’événements de vie stressants. Ces facteurs contribuent à déterminer une vulnérabilité individuelle dont la lecture diachronique, aux différentes périodes de la vie, permet d’éclairer les mécanismes complexes d’interactions gènes-environnement. Les populations les plus vulnérables, en termes de sévérité, d’impact et de comorbidités de la maladie sont représentées par l’adolescent et le jeune adulte, la femme en période puerpérale, et le sujet âgé. Nous apporterons également des éléments relatifs aux périodes péri-ménopausiques, ainsi que sur les données relatives aux dépressions du milieu de la vie.

Major depression is a common, severe, chronic, and often life-threatening illness. There is a growing body of evidence that, far from being a disease with purely psychological manifestations, major depression is a systemic disease with deleterious effects on multiple organ systems. Stressful life events have a substantial causal association with depression, and there is now compelling evidence that even early life stress constitutes a major risk factor for the subsequent development of depression. This review will focus on the association between severity of depression and diachronic vulnerability across the life-span, in terms of events of life, stress, and hormonal modulation, with a special focus on depression in young adults, women during postpartum and in depression in ederly people. Given the high prevalence of depressive disorders, the significant burden and the severity of disease in adolescents and young adults experiencing their first episode, they represent a group at high risk of relapse, recurrence, comorbidity and suicide to whom early intervention and prevention efforts should be targeted. Females exhibit different stress sensitivities than males which might contribute to their increased vulnerability for depression and the disease exhibit a prevalence among women which is 2-3x higher than in men. The postpartum period is considered the time of greatest risk for women to develop major depression and postpartum depression affects approximately 15% of women. In old age, depression mainly affects those with chronic medical illness, severe disability or mental decline. Depression in elderly worsens the outcomes of many medical illness and increases mortality. Environmental factors, such as isolation, caregiving and bereavement, contribute to further increase susceptibility to depression or triggering depression in already vulnerable elderly people. Suitable treatment of depression in elderly reduces the symptoms, prevents suicidal ideation, improves cognitive and functional status in order to improve the recovery of a good quality of life, as well as the mortality risk.