Abstract

Depression is a common disorder both in men and women, although its occurrence in women is higher. Women tend to encounter this disorder about two times more than men. The prevalence of depression during life span both in men and women would be about fifteen percent [1-3]. Two different types of depression would be endogenous and reactive ones and in both types, genetic and environmental factors are responsible for the occurrence of the disorder. Although there are various genes involved in affective disorders, specific genes which can be responsible for the occurrence of depression have not been identified. Environmental factors and also psychological ones play an important role in the development of depression. Depressive cognitions are very important in developing depression.