What is the Patient Health Questionnaire (PHQ-9) and how does it work?

Released in 2010 by Pfizer, the PHQ-9 is a simple 9-question instrument for screening, diagnosing, monitoring and measuring the severity of depression. In less than 10 years, it has become one of the most commonly used depression screens by clinicians as well as researchers alike, and is endorsed by a number of organizations, such as the American Psychological Association (APA), the National Institute for Health and Care Excellence, and the American Psychiatric Association. While the PHQ-9 is most commonly used by mental health providers, a wide array of other healthcare providers (such as Primary Care Physicians, for example) have also adopted this questionnaire as part of their standard practices for screening depression symptoms.

How it works

At the beginning of the PHQ-9, patients are prompted with the following question: “How often have you been bothered by the following over the past 2 weeks?” Patients then fill out the following questionnaire:

Once these questions are answered by the patient, the assessment is scored and the severity of the depressive symptoms are categorized according to the following rules:

In the example responses above, the final score would be: 3 + 1 + 2 + 3 + 1 + 2 + 3 + 0 + 1 = 16 / 27, which would classify the depressive symptoms as being “moderately severe”.

Note: The purpose of a PHQ-9 is to assist the clinician in quantifying depressive symptoms and monitoring the severity of these symptoms over time. Any conclusions drawn from the PHQ-9 should be paired with clinical interviews and observations, other mental health examinations or assessments administered, and evaluations of the patient’s level of distress, functional impairment, and/or family history. Please refer to the official PHQ-9 instruction manual for additional details.