Is depression caused by life events?
Both schizofrenia and depression are linked to a genetic predisposition and life events. Individuals with no genetic predisposition may become depressed when the trigger is sufficiently intense, while individuals with genetic predisposition may become depressed in the absence of clear life events triggering the depression (Kendler et al, 1995).

Reference
- Kendler et al, Am J Psychiatry (1995); 152(6): 833-42