Depression is a serious medical illness. It's more than just a feeling of being sad or "blue" for a few days. If you are one of the more than 19 million teens and adults in the United States who have depression, the feelings do not go away. They persist and interfere with your everyday life. Symptoms can include
Feeling sad or "empty"
Loss of interest in favorite activities
Overeating, or not wanting to eat at all
Not being able to sleep, or sleeping too much
Feeling very tired
Feeling hopeless, irritable, anxious, or guilty
Aches or pains, headaches, cramps, or digestive problems
Thoughts of death or suicide
Depression is a disorder of the brain. There are a variety of causes, including genetic, biological, environmental, and psychological factors. Depression can happen at any age, but it often begins in teens and young adults. 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, talk therapy, or both.
NIH: National Institute of Mental Health