Apparently additional factors, possibly a stressful environment, are involved in its onset.
Major depression also seems to occur, generation after generation, in some families. However, it can occur in people with no family history of the illness as well.
Psychological makeup also plays a role in vulnerability to depression. People with low self-esteem, who consistently view themselves and the world with pessimism or who are readily overwhelmed by stress, are prone to depression.
A serious loss, chronic illness, difficult relationship, financial problem, or any other unwelcome change in life patterns can also trigger a depressive episode. Very often, a combination of genetic, psychological, and environmental factors is involved in the onset of a depressive disorder.
Treatments can include, antidepressant medications, psychotherapy, and support groups. Any one or a combination of these treatments are used to battle these illnesses. Treatment choice will depend on the severity and type of illness. Electroconvulsive Therapy may be used in extreme cases that are high risk for suicide and do not respond to medication.