Evaluation by a trained healthcare provider is necessary for diagnosing and treating depression. But the standard psychiatry reference book (DSM-IV) criteria for Major Depression is 5 or more for the following symptoms for at least 2 months:
1. Depressed mood for most of the day
2. Decreased interest in hobbies and activities
3. Insomnia or hypersomnia
4. Significant weight loss or gain
5. Psychomotor agitation or slowing
6. Decreased energy, persistent feelings of tiredness
7. Feelings of worthlessness or excessive guilt
8. Inability to concentrate or increasing forgetfullness
9. Recurrent thoughts of death