Depression (major depressive disorder) is a common and serious medical illness that negatively affects how you feel, the way you think and how you act. Fortunately, it is also treatable. Depression causes feelings of sadness and/or a loss of interest in activities once enjoyed. It can lead to a variety of emotional and physical problems and can decrease a person’s ability to function at work and at home.
Depression symptoms can vary from mild to severe and can include:
- Feeling sad or having a depressed mood
- Loss of interest or pleasure in activities once enjoyed
- Changes in appetite — weight loss or gain unrelated to dieting
- Trouble sleeping or sleeping too much
- Loss of energy or increased fatigue
- Increase in purposeless physical activity (e.g., hand-wringing or pacing) or slowed movements and speech (actions observable by others)
- Feeling worthless or guilty
- Difficulty thinking, concentrating or making decisions
- Thoughts of death or suicide
Symptoms must last at least two weeks for a diagnosis of depression.
Also, medical conditions (e.g., thyroid problems, a brain tumor or vitamin deficiency) can mimic symptoms of depression so it is important to rule out general medical causes.
Depression affects an estimated one in 15 adults (6.7%) in any given year. And one in six people (16.6%) will experience depression at some time in their life. Depression can strike at any time, but on average, first appears during the late teens to mid-20s. Women are more likely than men to experience depression. Some studies show that one-third of women will experience a major depressive episode in their lifetime.
Depression Is Different From Sadness or Grief/Bereavement
The death of a loved one, loss of a job or the ending of a relationship are difficult experiences for a person to endure. It is normal for feelings of sadness or grief to develop in response to such situations. Those experiencing loss often might describe themselves as being “depressed.”
But being sad is not the same as having depression. The grieving process is natural and unique to each individual and shares some of the same features of depression. Both grief and depression may involve intense sadness and withdrawal from usual activities. They are also different in important ways:
- In grief, painful feelings come in waves, often intermixed with positive memories of the deceased. In major depression, mood and/or interest (pleasure) are decreased for most of two weeks.
- In grief, self-esteem is usually maintained. In major depression, feelings of worthlessness and self-loathing are common.
- For some people, the death of a loved one can bring on major depression. Losing a job or being a victim of a physical assault or a major disaster can lead to depression for some people. When grief and depression co-exist, the grief is more severe and lasts longer than grief without depression. Despite some overlap between grief and depression, they are different. Distinguishing between them can help people get the help, support or treatment they need.
Risk Factors for Depression
Depression can affect anyone—even a person who appears to live in relatively ideal circumstances.
Several factors can play a role in depression:
- Biochemistry: Differences in certain chemicals in the brain may contribute to symptoms of depression.
- Genetics: Depression can run in families. For example, if one identical twin has depression, the other has a 70 percent chance of having the illness sometime in life.
- Personality: People with low self-esteem, who are easily overwhelmed by stress, or who are generally pessimistic appear to be more likely to experience depression.
- Environmental factors: Continuous exposure to violence, neglect, abuse or poverty may make some people more vulnerable to depression.