The PHQ-9 and GAD-7: Brief Screening Measures for Depression and Anxiety

The Patient Health Questionnaire-9 (PHQ-9) and the Generalized Anxiety Disorder 7-item scale (GAD-7) were both developed by Drs. Robert Spitzer, Kurt Kroenke, and Janet Williams as part of the larger Patient Health Questionnaire (PHQ) system, a self-administered version of the PRIME-MD diagnostic instrument designed for use in primary care settings.

The PHQ-9 was published in 2001 (Kroenke, Spitzer, & Williams, 2001, Journal of General Internal Medicine). Its nine items correspond directly to the nine DSM-5 diagnostic criteria for major depressive disorder, making it both a severity measure and a tool that can assist in diagnostic assessment.

The GAD-7 followed in 2006 (Spitzer, Kroenke, Williams, & Lowe, 2006, Archives of Internal Medicine). Although named for generalized anxiety disorder, it has demonstrated good sensitivity across multiple anxiety disorders, including panic disorder, social anxiety disorder, and PTSD, making it a useful general anxiety screener.

Both instruments are in the public domain and require no licensing fees, which has contributed significantly to their widespread adoption. They are among the most cited screening instruments in the psychiatric literature.

PHQ-9: Internal consistency is excellent (Cronbach's alpha 0.86-0.89). Test-retest reliability is strong (intraclass correlation 0.84). At a cutoff score of 10, the PHQ-9 has a sensitivity of 88% and specificity of 88% for major depressive disorder (Kroenke et al., 2001). It performs comparably to clinician-administered instruments like the Hamilton Depression Rating Scale.

GAD-7: Internal consistency is excellent (Cronbach's alpha 0.92). At a cutoff score of 10, the GAD-7 has a sensitivity of 89% and specificity of 82% for generalized anxiety disorder (Spitzer et al., 2006). It also demonstrates good operating characteristics as a screener for panic disorder (sensitivity 74%), social anxiety disorder (sensitivity 72%), and PTSD (sensitivity 66%).

Both instruments use the same four-point Likert scale for the past two weeks: Not at all (0), Several days (1), More than half the days (2), Nearly every day (3).

PHQ-9 scoring (range 0-27): 0-4 Minimal, 5-9 Mild, 10-14 Moderate, 15-19 Moderately Severe, 20-27 Severe. A score of 10 or above is the standard threshold for clinically significant depression.

GAD-7 scoring (range 0-21): 0-4 Minimal, 5-9 Mild, 10-14 Moderate, 15-21 Severe. A score of 10 or above is the standard threshold for clinically significant anxiety.

These are screening instruments, not diagnostic tools. A score above threshold indicates the need for further clinical evaluation but does not constitute a diagnosis. Conversely, a score below threshold does not rule out a disorder.

Item 9 of the PHQ-9 asks about thoughts of self-harm or being better off dead. Any endorsement of this item (a score of 1, 2, or 3) should trigger a follow-up safety assessment, regardless of the total score. This is standard clinical practice across all treatment settings.

The presence of suicidal ideation on Item 9 does not by itself indicate imminent risk, but it requires further evaluation using a structured risk assessment protocol. If you or someone you know is in crisis, contact the 988 Suicide and Crisis Lifeline by calling or texting 988.

Initial screening: Both instruments are routinely administered at intake to establish a baseline severity level. Many integrated care settings administer the PHQ-9 and GAD-7 together as a combined depression and anxiety screen.

Treatment monitoring: Serial administration at regular intervals (every session, biweekly, or monthly) allows clinicians to track symptom trajectory. A change of 5 or more points on the PHQ-9 is generally considered a clinically meaningful change (reliable change index). The same threshold is commonly applied to the GAD-7.

Outcome measurement: Both instruments are widely used as primary outcome measures in clinical trials and quality improvement programs. Their brevity, public domain status, and strong psychometrics make them among the most practical tools available in clinical practice.

Measurement-based care: The systematic use of these instruments to guide treatment decisions (dose adjustments, modality changes, referrals) is a growing standard of care. The STAR*D trial and subsequent research have demonstrated that measurement-based care produces better outcomes than treatment as usual.