Reactive depression, or grief reaction, occurs after the loss of a loved one, job or some important opportunity is very common. This usually lessens with time. The loss of a close friend or relative brings on this kind of emotional reaction. Biochemical or endogenous depression is caused by a disturbance in the body's chemical system. Negative and faulty thinking is the root of most depression.
Unrealistic expectations cause depression.
This in turn reinforces a poor self-concept and further aggravates the depression. If your behavior is contrary to your moral standards or your value system this can result in depression. It produces real guilt, and guilt is a component in depression. Success, achieving a high goal, gaining a valued position with the demands for higher level of performance can be threatening and lead to depression. Postpartum blues after the birth of a child may lead to depression.