Although we all feel sad sometimes, clinical (major) depression is diagnosed when a person experiences depressed mood (sadness), loss of interest or pleasure in daily activities, plus some of the following symptoms for at least 2 weeks:
- changes in appetite or weight
- lack of motivation or energy
- insomnia (trouble sleeping) or oversleeping
- noticeable changes in activity level (agitated or slowed down)
- feelings of worthlessness or guilt
- difficulty concentrating or making decisions
- recurring thoughts of death or suicide
Clinical depression may vary in its severity, and in its extreme forms (i.e., thoughts of suicide) can be life-threatening and require immediate medical attention.
Symptoms of other forms of depression, although generally milder, may still negatively affect a person's daily activities and quality of life.