Depression is a type of psychiatric disorder that is characterized by constant feelings of sadness and lack of interest in activities that previously gave pleasure to the affected person. Depression affects the feeling, behavior and thinking of a person. Depression is of various types including Major depression or Major depressive disorder, Dysthymic disorder or dysthymia, Minor depression, Psychotic depression, postpartum depression and Seasonal affective disorder (SAD). Bipolar disorder is a psychiatric disorder that is characterized by cyclic episodes of mania and depression. The signs and symptoms of depression depend upon the type and severity of depression. The patient feels constantly sad, anxious, empty, hopeless, restless, and irritable. There is lack of interest in activities, which were once pleasurable. Symptoms of generalized tiredness and fatigue may be present along with sleep disturbances, memory and concentration problems and change in eating habits. In more severe cases, the patient may develop thoughts to commit suicide.