If you or someone you know is experiencing one or more of the symptoms below for more than two weeks, consider getting more information and help:
In adults: 
- Confused thinking
- Long-lasting sadness or irritability
- Extreme highs and lows in mood
- Excessive fear, worry or anxiety
- Social withdrawal
- Dramatic changes in eating or sleeping habits
- Strong feelings of anger
- Delusions or hallucinations (seeing or hearing things that others do not)
- Increasing inability to cope with daily problems and activities
- Thoughts of suicide
- Denial of obvious problems
- Many unexplained physical problems
- Abuse of drugs and/or alcohol
In older children and pre-teens:
- Abuse of drugs and/or alcohol
- Inability to cope with daily problems and activities
- Changes in sleeping and/or eating habits
- Excessive complaints of physical problems
- Defying authority, skipping school, stealing or damaging property
- Intense fear of gaining weight
- Long-lasting negative mood, often along with poor appetite and thoughts of death
- Frequent outbursts of anger
In younger children:
- Changes in school performance
- Poor grades despite strong efforts
- Excessive worry or anxiety
- Hyperactivity
- Persistent nightmares
- Persistent disobedience and/or aggressive behavior
- Frequent temper tantrums
Courtesy of WebMD