Major Depressive Disorder is a mental illness that may have symptoms of:
- sadness, despair or hopelessness
- lack of energy and enthusiasm
- loss of interest in things previously enjoyed
- changes in sleep patterns - insomnia or sleeping too much (hypersomnia)
- weight loss or weight gain
- unexplained crying
- thoughts of suicide
- body aches
- social withdrawal
- trouble concentrating, remembering, or making decisions
A person can't have both major depression and bipolar disorder. A person with major depression does not experience mania or hypomania.
However, the symptoms of bipolar depression (unmixed) and major depression are the same. For more on the depressive symptoms, see Warning Signs of Depression.

