Depression is a common but serious medical condition that negatively affects a person's mood, energy levels, concentration and overall outlook on life, according to the National Institute of Mental Health. There are different forms of depression, and experts suggest that causes for depressive disorders include genetic, environmental, psychological and biological factors.
Common depressive disorders include major depression, bipolar disorder and persistent depressive disorder, explains the National Institute of Mental Health. With major depression, an individual may have depressive tendencies that severely impact her ability to enjoy life. Eating, sleeping and working may all be affected by major depression, and typically those with major depression have several depressive episodes in a lifetime. Bipolar disorder, though not as common as major depression, involves constant mood swings where an individual fluctuates from manic episodes of feeling extremely happy to low periods of severe depression. Persistent depressive disorder lasts at least two years and may include episodes of major depression as well as less severe episodes.
Generally, individuals with depressive disorders display symptoms of persistent sadness, hopelessness, guilt, irritability, fatigue, insomnia or thoughts of suicide, notes the National Institute of Mental Health. Depression is typically diagnosed by a physician or mental health professional following a physical exam and psychological evaluation. Common treatments for depression include antidepressants, tricyclics, monoamine oxidase inhibitors and psychotherapy.