Depression is a psychological state characterized by persistent low mood. It is normal to have periods of low mood sometimes, such as at the passing of a loved one. Low mood becomes a concern when it does not lessen over time, or when it occurs in the absence of a trigger.
Other symptoms associated with depression include
- Loss of interest or enjoyment of previously enjoyable activities
- Eating more (hyperphagia) or less (hypophagia) than usual
- Difficulty sleeping (insomnia) or sleeping too much (hypersomnia)
- Feeling tired
- Difficulty concentrating
- Feelings of worthlessness or guilt
- Suicidal thoughts
Clinically diagnosable disorders involving depression include
- Major depressive disorder (MDD): clinically significant depression symptoms for two weeks or more.
- Persistent depressive disorder (Dysthymia, or chronic depression): depression lasting at least two years. Symptoms are generally less severe than MDD.
- Bipolar disorders: characterised by episodes of depressed and abnormally elevated mood (e.g. mania, hypomania)