The PHQ-9 (Patient Health Questionnaire-9) is the undisputed gold standard for depression screening in outpatient medicine.
Screening and Tracking
Because depression is an invisible disease, clinicians need a reliable, numeric way to track whether a patient is improving on antidepressants. The PHQ-9 assigns a score of 0 (Not at all) to 3 (Nearly every day) for each of the core DSM-5 symptoms of depression experienced over the prior two weeks.
The Diagnostic Criteria (SIGECAPS)
The questionnaire covers:
- Sleep: Insomnia or sleeping too much.
- Interest: Little interest or pleasure in doing things (Anhedonia).
- Guilt: Feeling bad about yourself or feeling like a failure.
- Energy: Feeling tired or having little energy.
- Concentration: Trouble focusing on reading or TV.
- Appetite: Poor appetite or overeating.
- Psychomotor: Moving/speaking very slowly, or being severely restless.
- Suicidality: Thoughts of death or self-harm.
Sum of scores (0-3) across 9 questions over the past 2 weeks.
A score ≥ 10 is the universally accepted threshold indicating a likely diagnosis of Major Depressive Disorder, prompting the initiation of therapy or medication.