According to the DSM-IV, a manual used to diagnose mental disorders, depression occurs when you have at least five of the following nine symptoms at the same time:
- a depressed mood during most of the day, particularly in the morning
- fatigue or loss of energy almost every day
- feelings of worthlessness or guilt almost every day
- impaired concentration, indecisiveness
- insomnia or hypersomnia (excessive sleeping) almost every day
- markedly diminished interest or pleasure in almost all activities nearly every day
- recurring thoughts of death or suicide (not just fearing death)
- a sense of restlessness — known as psychomotor agitation — or being slowed down — retardation
- significant weight loss or gain (a change of more than 5% of body weight in a month)