Depression can affect anyone—even a person who appears to live in relatively ideal circumstances.
Several factors can play a role in depression:
Differences in certain chemicals in the brain may contribute to symptoms of depression.
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.
People with low self-esteem, who are easily overwhelmed by stress, or who are generally pessimistic appear to be more likely to experience depression.
Continuous exposure to violence, neglect, abuse or poverty may make some people more vulnerable to depression.