According to the National Institute of Mental Health, depression is a mental disorder or illness that can present itself in several forms. The form of depression that a person suffers from depends on genetic, environmental, biological and psychological factors.
Depressive disorders are disorders that affect the brain, states the National Institute of Mental Health. When a person suffers from a depressive disorder the portions of their brain that involve mood, sleep, thinking, appetite and behavior become altered. When a person has a depressive disorder they may feel sad, anxious, hopeless, irritable, guilty, worthless, restless or helpless. They may also have aches and pains and a loss of interest in their everyday activities. These symptoms all arise due to changes in brain chemistry. Patients who suffer from depressive disorders may need counseling or antidepressant medications to get well states the National Institute of Mental Health.