* Loss of interest or pleasure in activities you used to enjoy
* Change in weight
* Difficulty sleeping or oversleeping
* Energy loss
* Feelings of worthlessness
* Thoughts of death or suicide
Depression can run in families, and usually starts between the ages of 15 and 30. It is much more common in women. Women can also get postpartum depression after the birth of a baby. Some people get seasonal affective disorder in the winter. Depression is one part of bipolar disorder.
There are effective treatments for depression, including antidepressants and talk therapy. Most people do best by using both.
NIH: National Institute of Mental Health