Diagnostic criteria for major depressive disorder (Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition)
| Five or more of the following symptoms during the same 2-week period, with the symptoms representing a change from previous functioning and with at least one of the symptoms being either depressed mood or loss of interest or pleasure in activities of daily life. |
| 1. Depressed mood most of the day, nearly every day, as indicated by either subjective report (e.g., feels sad, empty, or hopeless) or observation made by others (e.g., appears tearful). (In children and adolescents, a depressed mood can be an irritable mood.) |
| 2. Markedly diminished interest or pleasure in all, or almost all, activities most of the day, nearly every day (as indicated by either subjective account or observation). |
| 3. Significant weight loss when not dieting or weight gain (e.g., a change of >5% of body weight in a month), or decrease or increase in appetite nearly every day. (In children, failure to gain expected weight should be considered.) |
| 4. Insomnia or hypersomnia nearly every day. |
| 5. Psychomotor agitation or retardation nearly every day (observable by others, not merely subjective feelings of restlessness or being slowed down). |
| 6. Fatigue or loss of energy nearly every day. |
| 7. Feelings of worthlessness or excessive or inappropriate guilt (which may be delusional) nearly every day (not merely self-reproach or guilt about being sick). |
| 8. Diminished ability to think or concentrate, or indecisiveness, nearly every day (either by subjective account or as observed by others). |
| 9. Recurrent thoughts of death (not just fear of dying), recurrent suicidal ideation without a specific plan, or a suicide attempt or a specific plan for committing suicide. |