Here is the diagnostic criteria for Dysthymia, a lighter form of depression. 

Depressed mood most of the day for more days than not, for at least 2 years, and the presence of two or more of the following symptoms that cause clinically significant impairment in social, work, or other important areas of functioning:

1. Poor appetite or overeating

2. Insomnia or sleeping too much

3. Low energy or fatigue

4. Low self esteem

5. Poor concentration or difficulty making decisions

6. Feeling hopelessness