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 PHQ-8 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)

How to administer the PHQ-8

The PHQ-8 is a self-report questionnaire. Respondents rate each of the eight items themselves based on how often they have been bothered by the symptom over the past two weeks. No clinician administration is required, which makes it practical for large-scale surveys and routine outcome monitoring.

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

PHQ-8 scoring and interpretation

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). In 198,678 US survey respondents, the prevalence of current depression was similar whether defined by the PHQ-8 diagnostic algorithm or a score of 10 or more (9.1% vs. 8.6%); of respondents scoring 10 or more, only 3.5% had no evidence of depressive disorder or depressive symptoms.
• Reliability and cross-country equivalence have been examined across 27 European countries (Arias de la Torre et al., 2023)
• 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

Limitations

• Screening, not diagnosis. A score at or above 10 indicates a need for further clinical assessment; diagnosis requires a comprehensive clinical evaluation.
• No suicidality item. The PHQ-8 does not screen for thoughts of self-harm or suicide, so suicidal ideation must be assessed separately. For individual patient monitoring, the PHQ-9 is generally preferred.
• Criterion standard in the general-population study. Kroenke et al. (2009) compared the cutoff with the PHQ-8 diagnostic algorithm rather than an independent structured psychiatric interview.
• Self-report. Scores depend on the respondent's recall over two weeks and willingness to disclose.

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.