Your PHQ-9 score falls into one of five severity categories: minimal (0–4), mild (5–9), moderate (10–14), moderately severe (15–19), or severe (20–27). A score of 10 or higher is commonly used as the clinical threshold that warrants further evaluation and possible treatment. Beyond the total score, pay attention to question 9 (thoughts of self-harm or death). Any positive response to this item — even "several days" — should prompt a direct conversation with a healthcare provider about safety, regardless of the overall score. The PHQ-9 is also useful for tracking changes over time; a decrease of 5 or more points generally indicates clinically meaningful improvement.

The PHQ-9 is appropriate for initial depression screening in primary care, behavioral health, and community settings. The U.S. Preventive Services Task Force (USPSTF) recommends depression screening for all adults, and the PHQ-9 is one of the most widely used instruments for this purpose. It is also valuable for monitoring treatment response — repeating the PHQ-9 every 2–4 weeks after starting or adjusting antidepressant therapy provides an objective measure of whether the patient is improving. Many clinical practices and research trials use serial PHQ-9 scores as a primary outcome measure.

The PHQ-9 is a screening tool, not a diagnostic instrument. A high score does not confirm a diagnosis of major depressive disorder — formal diagnosis requires a clinical interview assessing DSM criteria, duration, functional impairment, and exclusion of other causes (e.g., hypothyroidism, substance use, grief). The questionnaire relies on self-report over the past two weeks, which introduces recall bias. Patients may minimize or exaggerate symptoms depending on their comfort level, cultural background, or the setting. Somatic symptoms of depression (fatigue, appetite changes, sleep problems) overlap with many medical conditions, which can inflate scores in medically ill patients. The PHQ-9 has been validated across many populations but performs less reliably in certain groups, including adolescents (for whom the PHQ-A is preferred), older adults with cognitive impairment, and patients with limited health literacy.