There is no single cause for depression, but research suggests four factors from which it likely results: genetic, biochemical, psychological and environmental.
While scientists haven't discovered a "depression gene," they have seen evidence based on family histories suggesting there may be a genetic link. Children of people with major depression are more likely to experience depression than the general population. But because depression also occurs in individuals without family histories of the illness, researchers continue to study additional factors.
Research with magnetic resonance imaging (MRI) reveals that depressive illnesses are brain disorders. The brains of people with depression have abnormal levels of brain chemicals called neurotransmitters, the messengers between the brain and the body.
Psychological factors also come into play. People with certain characteristics such as pessimism and low self-esteem have a tendency to develop depression. These characteristics, combined with environmental stressors such as relationships, illness, financial problems or major life events, contribute to patterns of depressive illness. Depression's onset is frequently a combination of these causes.
Next, we'll discuss how mood disorders are diagnosed, including a look into a video game that may help detect depression.