PHQ-9 Depression Score Calculator

What Is the PHQ-9?

The Patient Health Questionnaire-9 (PHQ-9) is a validated, self-administered screening and severity tool for major depressive disorder (MDD). Developed by Kroenke, Spitzer, and Williams in 2001, it operationalises the nine DSM-5 diagnostic criteria for depression into a brief questionnaire that takes under 3 minutes to complete. It is the most widely used depression screening tool in primary care globally.

Each item is scored 0–3 based on frequency over the past two weeks, giving a maximum score of 27. A PHQ-9 score ≥10 has a sensitivity and specificity of 88% each for major depressive disorder (Kroenke et al., 2001).

PHQ-9 Score Interpretation

The 9 DSM-5 Criteria Measured by PHQ-9

Each PHQ-9 item directly maps to a DSM-5 criterion for major depressive disorder. For a provisional MDD diagnosis, at least 5 of these 9 criteria must be present for most of the day, nearly every day, over 2 weeks — and one of them must be either depressed mood (Q2) or anhedonia (Q1):

PHQ-9 Validity and Reliability

The PHQ-9 has been validated in over 8,000 patients across primary care and obstetrics/gynaecology settings. Key psychometric properties include high internal consistency (Cronbach's alpha 0.86–0.89) and excellent test-retest reliability (r = 0.84). Using a cut-off of ≥10, it demonstrates 88% sensitivity and 88% specificity for major depressive disorder against structured psychiatric interview (Kroenke et al., 2001).

The PHQ-9 has been validated across multiple languages, cultures, and clinical settings including primary care, hospital medicine, oncology, cardiology, and obstetrics. It is endorsed by NICE (CG90, 2022), WHO, and forms part of the NHS IAPT (Improving Access to Psychological Therapies) programme minimum dataset.

Important Clinical Notes

Frequently Asked Questions

What PHQ-9 score indicates depression?

A score of ≥10 is the standard clinical threshold for major depressive disorder, with 88% sensitivity and 88% specificity. However, clinical context matters — a score of 8–9 with significant functional impairment (Q10) and both core symptoms present (Q1 and Q2) may still warrant treatment. Scores should always be interpreted alongside a full clinical assessment.

How is PHQ-9 used to monitor treatment response?

The PHQ-9 is an excellent treatment monitoring tool. A reduction of ≥5 points is considered a clinically meaningful response. A score falling below 10 is a "partial response." A score below 5 represents remission. Repeat PHQ-9 at 2–4 weeks after initiating treatment and monthly thereafter. If score has not reduced by ≥50% at 6–8 weeks, consider dose adjustment or medication change.

Can PHQ-9 be used in patients with medical illness?

Yes, but with caution. Somatic symptoms (fatigue, sleep disturbance, appetite change) overlap significantly with many medical conditions — hypothyroidism, anaemia, chronic pain, cancer, and post-MI states. This can inflate PHQ-9 scores in medically unwell patients. Some clinicians prefer to use the cognitive/affective subscale (Q1, Q2, Q6, Q7, Q9) in medically ill patients to reduce somatic confounding. Always consider and exclude medical causes before attributing symptoms to depression.

References

1. Kroenke K, Spitzer RL, Williams JBW. The PHQ-9: Validity of a brief depression severity measure. J Gen Intern Med. 2001;16(9):606-613.
2. Kroenke K, Spitzer RL. The PHQ-9: A new depression diagnostic and severity measure. Psychiatr Ann. 2002;32:509-521.
3. NICE CG90. Depression in adults: recognition and management. Updated 2022. National Institute for Health and Care Excellence.
4. Spitzer RL, Kroenke K, Williams JBW, et al. A brief measure for assessing generalised anxiety disorder: the GAD-7. Arch Intern Med. 2006;166:1092-1097.
5. American Psychiatric Association. Diagnostic and Statistical Manual of Mental Disorders, 5th edition (DSM-5). 2013.