How many symptoms must be present, and for how long, before major depressive disorder is diagnosed?

1. Diagnosis requires a total of five symptoms present for at least a two-week period. 2. At least one of those must be depressed mood most of the day nearly every day, or loss of interest and pleasure in usual activities. 3. The remaining symptoms are drawn from appetite or weight change, sleep disturbance, psychomotor change, fatigue, worthlessness, poor concentration and suicidal ideation. 4. The symptoms must cause significant distress or impair functioning, and must not be caused by substances or a medical condition. 5. Two years of depressed mood with two further symptoms describes persistent depressive disorder instead. _Source: OpenStax Psychology (1st ed., CC BY 4.0), Ch 15 "Psychological Disorders", section 15.7 Mood Disorders_