PHQ-8: Patient Health Questionnaire, Depression Scale

About the PHQ-8

The Patient Health Questionnaire-8 (PHQ-8) is an 8-item self-report measure of depression severity derived from the PHQ-9 by omitting item 9 (thoughts of self-harm or suicide). It was validated by Kroenke and colleagues as a measure of current depression suitable for large-scale surveys, epidemiological research, and clinical settings where suicidality screening occurs through a separate process.

The PHQ-8 and PHQ-9 use identical items for questions 1–8 and share the same scoring structure, thresholds, and clinical interpretations. The only difference is the absence of item 9, which makes the PHQ-8 appropriate for self-administered surveys and contexts where clinicians prefer to assess suicidal ideation through direct conversation rather than questionnaire.

What the Assessment Measures

Both the PHQ-8 and PHQ-9 measure the nine DSM criteria for major depressive disorder. The PHQ-8 covers eight of these:

1. Little interest or pleasure in doing things
2. Feeling down, depressed, or hopeless
3. Trouble falling or staying asleep, or sleeping too much
4. Feeling tired or having little energy
5. Poor appetite or overeating
6. Feeling bad about yourself
7. Trouble concentrating
8. Moving or speaking slowly (or the opposite, restless or fidgety)

Each item is rated on a 0–3 frequency scale over the past two weeks:

• 0, Not at all
• 1, Several days
• 2, More than half the days
• 3, Nearly every day

Scoring

Total score range: 0–24

A score of ≥10 is the standard cutoff for probable major depression, with sensitivity and specificity both approximately 88% compared to structured diagnostic interview.

When to Use the PHQ-8 vs. PHQ-9

The PHQ-9 remains the standard for clinical measurement-based care, as it includes suicidal ideation screening. The PHQ-8 is preferred when:

• Suicidality is assessed separately or through clinical interview
• Population-based surveys require a measure that doesn't require clinical follow-up for all positive screens
• Comparing data to large epidemiological studies that used the PHQ-8

For individual patient monitoring in clinical practice, the PHQ-9 is generally recommended to ensure suicidal ideation is not missed.

Psychometric Properties

• Validated in large nationally representative samples (Kroenke et al., 2009)
• PHQ-8 and PHQ-9 scores are nearly identical in datasets where item 9 is rarely endorsed
• Strong internal consistency (Cronbach's α ≈ 0.86)
• Sensitivity ≈ 88%, specificity ≈ 88% for major depression diagnosis at cutoff ≥10

Functional Impairment Item

Both the PHQ-8 and PHQ-9 include a supplemental item asking how difficult the reported symptoms have made it to do work, handle home responsibilities, and get along with others (rated: Not difficult at all / Somewhat difficult / Very difficult / Extremely difficult). This item is not scored but aids clinical interpretation.

References

• Kroenke K, Strine TW, Spitzer RL, et al. (2009). The PHQ-8 as a measure of current depression in the general population. Journal of Affective Disorders, 114(1–3), 163–173. PMID: 18752852
• Kroenke K, Spitzer RL, Williams JB, Löwe B. (2010). The Patient Health Questionnaire Somatic, Anxiety, and Depressive Symptom Scales: a systematic review. General Hospital Psychiatry, 32(4), 345–359. PMID: 20633738
• Spitzer RL, Kroenke K, Williams JB. (1999). Validation and utility of a self-report version of PRIME-MD: the PHQ primary care study. JAMA, 282(18), 1737–1744.