50%-80% of depressed patients experience a major life event during 3-6 months prior to the onset of depression. In comparison only 20%-30% of non depressed persons experience a major life event in the preceding 3-6 months. Approximately 20%-25% of persons who experience a stressful life event develop depression.
Stress also influences the clinical course of depression, due to continuing stress:
1. duration increases
2. symptoms can worsen
3. relapse is more likely
4. reduction of positive response.
These are the conclusions presented in a commentary in the JAMA:
Psychological stress and disease.
Authors: Cohen S, Janicki-Deverts D, Miller GE
Journal: JAMA, 298 (14): 1685-7, 2007
This interesting commentary also discusses the relationship between stress and other major diseases: cardiovascular disease, HIV/AIDS and cancer.
In the conclusion the authors rightly emphasize that stress is an important factor in depression. A clear causal relationship between stress and certain diseases is not yet established. The majority of individuals confronted with major life events and chronic stress remain disease-free. Genetic as well as psychological factors contributing to vulnerability to stress are under investigation.
Evidence is derived from prospective observational studies and natural experiments such as natural disasters, economic downsize, or bereavement