SAD appears to arise from a person's sensitivity to the limited amount of daylight that corresponds with seasonal changes. Symptoms typically begin in the fall, worsen in the winter, and improve in the spring. Dysthymia involves chronic symptoms that don't disable but prevent a person from feeling good. However, a person with dysthymia can have episodes of major depression as well. There is no single cause.
Some depressive episodes appear for no reason.
Diminished financial resources and social isolation also can be triggering circumstances. Finally, some depressive episodes are triggered by a stressful event, such as the death of a loved one, retirement, a move to a new area, or a health problem. In the case of a health problem, it's particularly important not to accept depression as a natural outcome of the illness. If you do, you may worsen your health condition and be less likely to take care of your physical, mental, and emotional needs. Bring any depressive symptoms to your doctor's attention and be assertive about getting treatment for depression, independent of the health problem.