Depression (also known as major depressive disorder, clinical depression, and major depression) is a mental illness characterized by persistently low mood, low self-esteem, and loss of interest or enjoyment in once-enjoyable activities. Depression is different from normal feelings of sadness in that depression lasts for weeks or even months. It often has no specific trigger.

Symptoms of depression can include:
  • Very low mood
  • Inability to get joy out of once-pleasurable activities
  • Feelings of worthlessness, guilt, and self-hate
  • Feelings of hopelessness
  • Insomnia, inability to fall asleep or stay asleep
  • Hypersomnia, sleeping too much
  • Change in appetite (either loss of appetite or increased appetite)
  • Thoughts of suicide

More than just a bout of the blues, depression isn't a weakness, nor is it something that you can simply "snap out" of. Depression may require long-term treatment. But don't get discouraged. Most people with depression feel better with medication, psychological counseling or both. Other treatments also may help.

Although depression may occur only one time during your life, usually people have multiple episodes of depression. During these episodes, symptoms occur most of the day, nearly every day and may include:

  • Feelings of sadness, emptiness or unhappiness
  • Angry outbursts, irritability or frustration, even over small matters
  • Loss of interest or pleasure in normal activities, such as sex
  • Sleep disturbances, including insomnia or sleeping too much
  • Tiredness and lack of energy, so that even small tasks take extra effort
  • Changes in appetite — often reduced appetite and weight loss, but increased cravings for food and weight gain in some people Anxiety, agitation or restlessness — for example, excessive worrying, pacing, hand-wringing or an inability to sit still
  • Slowed thinking, speaking or body movements
  • Feelings of worthlessness or guilt, fixating on past failures or blaming yourself for things that are not your responsibility
  • Trouble thinking, concentrating, making decisions and remembering things
  • Frequent thoughts of death, suicidal thoughts, suicide attempts or suicide
  • Unexplained physical problems, such as back pain or headaches

For some people, depression symptoms are so severe that it's obvious something isn't right. Other people feel generally miserable or unhappy without really knowing why.