Although its exact cause is unknown, dysthymia appears to have its roots in a combination of genetic, biochemical, environmental and psychological factors. In addition, chronic stress and trauma can provoke dysthymia.
Stress is believed to impair one's ability to regulate moods and prevent mild sadness from deepening and persisting. Social circumstances, particularly isolation and the unavailability of social support, also contribute to dysthymia. This cause can be especially debilitating given that depression often alienates those who are in a position to provide support, resulting in increased isolation and worsening symptoms. In old age, dysthymia is more likely to be the result of medical illness, cognitive decline, bereavement, and physical disability. In addition, trauma, loss of a loved one, a difficult relationship, or any stressful situation may trigger a depressive episode. Subsequent depressive episodes may occur with or without an obvious trigger.
Research indicates that depressive illnesses are disorders of the brain. Brain-imaging technologies, such as magnetic resonance imaging (MRI), have shown that the brains of people who have depression look different than those of people without depression. The parts of the brain responsible for regulating mood, thinking, sleep, appetite and behavior appear to function abnormally. In addition, important neurotransmitters—chemicals that brain cells use to communicate—appear to be out of balance. But these images do not reveal why the depression has occurred.
