Depression is a mood state that goes beyond temporarily feeling sad or blue. It is the most common mood disorder. It is a serious medical illness that affects one’s thoughts,feelings, behavior, mood and physical health. Depression is a life-long condition in which periods of wellness alternate with recurrences of illness.
Major depression is also known as clinical depression, major depressive illness, major affective disorder and unipolar mood disorder. It involves some combination of the following symptoms: depressed mood, poor concentration, insomnia, fatigue, appetite disturbances, excessive guilt, thoughts of suicide, feelings of hopelessness, irritability, loss of interest in activities, aches or pains, and overeating or appetitie loss. Left untreated, depression can lead to serious impairment in daily functioning and even suicide, which is the 10th leading cause of death in the U.S. Researchers believe that more than one-half of people who die by suicide are experiencing depression.

Anxiety disorders, such as post-traumatic stress disorder (PTSD), obsessive-compulsive disorder, panic disorder, social phobia, and generalized anxiety disorder, often accompany depression. PTSD may occur after a person experiences a terrifying event, such as a violent assault, a natural disaster, an accident, terrorism or military combat. These people are very likely to have co-existing depression.
Alcohol and other substance abuse or dependence may also co-exist with depression. Research shows that mood disorders and substance abuse commonly occur together.
Depression also may occur with other serious medical illnesses such as heart disease, stroke, cancer, HIV/AIDS, diabetes, and Parkinson's disease. People who have depression along with another medical illness tend to have more severe symptoms of both depression and the medical illness, more difficulty adapting to their medical condition, and more medical costs than those who do not have co-existing depression.

Depression is caused by a combination of genetic, biological, environmental, and psychological factors. Certain factors that can cause depression include: certain medication, abuse, conflict, death or a loss, genetics, serious illness, or substance abuse. Also, the hippocampus, which is involved in the storage of memory, appears to be smaller in those diagnosed with depression. Depression does seem to run in families. Children, siblings, and parents of people with severe depression are much more likely to suffer from depression than are members of the general population.

Depression is very treatable. The earlier the treatment begins, the better. Antidepressants primarily work on brain chemicals called neurotransmitters, especially serotonin and norepinephrine. Other antidepressants work on the neurotransmitter dopamine. Scientists have found that these particular chemicals are involved in regulating mood. Some of the newest and most popular antidepressants are called selective serotonin reuptake inhibitors (SSRIs). Fluoxetine (Prozac), sertraline
Zoloft), escitalopram (Lexapro), paroxetine (Paxil), and citalopram (Celexa) are some of the most commonly prescribed SSRIs for depression. Most are available in generic versions. Serotonin and norepinephrine reuptake inhibitors (SNRIs) are similar to SSRIs and include venlafaxine (Effexor) and duloxetine (Cymbalta).
Several types of psychotherapy—or "talk therapy"—can help people with depression. Two main types of psychotherapies—cognitive-behavioral therapy (CBT) and interpersonal therapy (IPT)—are effective in treating depression. CBT helps people with depression restructure negative thought patterns. Doing so helps people interpret their environment and interactions with others in a positive and realistic way. It may also help you recognize things that may be contributing to the depression and help you change behaviors that may be making the depression worse. IPT helps people understand and