Patient Health Questionnaire 9 (PHQ-9)
Recommended frequency: Every 2 weeks
Summary
The Patient Health Questionnaire 9 (“PHQ-9”) is a multi-purpose measure used to identify and monitor depression severity. It is a brief, 9-item version of the original PHQ assessment, which measures a variety of mental health challenges in addition to depression, such as anxiety, panic disorder, sleep disorders, and more. The PHQ-9 was co-created by Drs. Robert L. Spitzer, Janet W.B. Williams and Kurt Kroenke in 1999.
About the PHQ-9
The PHQ-9 combines depression diagnostic criteria from the Diagnostic and Statistical Manual of Mental Disorders, 4th edition (DSM-IV) with other leading major depressive symptoms. The key diagnostic symptom criteria adapted from the DSM-IV includes:
- Two typical signs of depression: anhedonia (referring to the inability or reduced ability to experience pleasure) and depressed mood;
- Cognitions (e.g. guilt/worthlessness and suicidality/thoughts of death); and
- Physical symptoms (e.g. change in appetite, difficulty sleeping and concentrating, feeling tired/slowed down or restless).
Each of the 9 questions rate the frequency of the symptoms, which factors into the severity index.
Clinicians and clinical leaders will often ask about the differences between the PHQ-9 and other depression scales. In comparison to the other commonly used depression scales (BDI, HAD-D, QIDS), the confidence intervals are quite similar, meaning they have all demonstrated reliability, validity, and are responsive to change. The PHQ-9 has a particularly high validity score, such that when PHQ-9 scores were above 10, the measure was shown to have a sensitivity of 88% and a specificity of 88% for Major Depressive Disorder—meaning that a score above 10 was a good indication that a diagnosis of depression would occur. Each of the major depression scales have their differences, although the PHQ-9 and BDI-II in particular tend to measure relatively equal levels of severity and track symptom change in a similar manner. The PHQ-9 is often preferred to other comparable assessments due to its brevity, which makes it easy to integrate into research or practice, and helps promote high completion rates.
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