Stress and affective disorders in humans.

A consistent body of findings published over 30 years shows raised rates of life events before onset of clinical unipolar depression. A range of threatening events is implicated, with only limited specificity, although a somewhat closer relationship to interpersonal losses. Social support both buffers effects of life events and its absence also has some independent stressful effects. Life stress also affects outcome. Effects extend across the age range, but are weaker or absent in recurrent disorder, particularly when this is severe or melancholic. They are also weaker in bipolar disorder, where social rhythm disruption may have a particular effect. The causative contribution of life stress is of moderate size overall but does not exclude many other factors. Causative chains are complex and life stress itself is not fully independent, because available social support is shaped by personal capacity to form relationships, and occurrence of life events has some genetic elements and is predicted by disturbance in childhood.