Depression is a mood disorder characterized mainly by prolonged and severe feelings of sadness associated with other symptoms and abnormal thinking and behavior, such as over-pessimistic ideas, lack of energy, sleep disturbance and appetite, or decreased interest and activity level. To distinguish a depressive disorder every passing state of sadness, the diagnosis of a psychiatrist is needed. There are several types of depressive disorders, by cause: endogenous depression, triggered by genetic or biological factors (hormonal changes or neurotransmitters that transmit nerve impulses in the brain); reactive depression generated by poor adaptation to external circumstances and environmental factors of strong emotional impact; minor depression or dysthymia, which are presented only some less intense symptoms normally associated with personality disorders and prolonged stress; or depression "masked", manifested by organic and functional disorders (somatization) and cardiovascular disorders, dizziness ... The therapist indicates what the best treatment for each person, but basically will focus on psychotherapy sessions.