Clinical depression — Major Depressive Disorder — requires at least five of nine specific symptoms, present most of the day, nearly every day, for at least two weeks. These include depressed mood, loss of interest or pleasure (anhedonia), sleep changes, appetite changes, fatigue, concentration difficulties, feelings of worthlessness, psychomotor changes, and in severe cases, thoughts of death. The symptoms must cause meaningful impairment.
Sadness is one symptom. Depression is a syndrome — a cluster of symptoms that travel together and persist. Someone who is sad still finds moments of joy. Someone who is depressed often cannot, no matter what positive events occur. That loss of pleasure — anhedonia — is one of the most diagnostically significant features.
Depression screening in primary care uses validated tools: the PHQ-9 is the standard. A score of 10 or higher warrants further evaluation. What the PHQ-9 does not capture is context, history, suicidality nuance, or the full clinical picture — which is why a positive screen leads to a conversation, not an automatic prescription.
Treatment depends on severity. Mild depression may respond to structured exercise, behavioral activation, and psychotherapy. Moderate-to-severe depression typically requires antidepressant medication, therapy, or both. SSRIs are first-line. Response takes 4–6 weeks. Inadequate response means reassessment — not failure.