Neither questionnaire is universally better for older adults. The GDS-15 was designed for older adults and limits somatic symptom content, whereas the PHQ-9 covers nine DSM-aligned symptom areas in a broad adult workflow. Choose the form supported for your population and setting, then follow any concerning result with clinical assessment.
How do the GDS-15 and PHQ-9 differ?
The two questionnaires sample the signs of late-life depression in different ways. Depression is not a normal part of aging, and it may not present mainly as sadness. The National Institute on Aging advises clinicians and families to look for changes in interest, sleep, appetite, energy, concentration, movement, hopelessness, and functioning.
| Feature | GDS-15 | PHQ-9 |
|---|---|---|
| Intended use | Depression screening developed for older adults | Adult depression symptom screening |
| Format | 15 yes-or-no questions about the past week | 9 frequency-rated questions about the past 2 weeks |
| Total | 0 to 15 | 0 to 27 |
| Symptom focus | Mostly mood, outlook, interest, activity, and life satisfaction | DSM-aligned symptom areas, including physical symptoms |
| Main tradeoff | Less somatic content, but not free of health-related overlap | Broader symptom coverage, with more somatic overlap |
The GDS-15 does not remove all medical overlap, because it still includes energy and activity. The PHQ-9 includes sleep, fatigue, appetite, and movement changes. Neither questionnaire can determine the cause: medical illness, medication effects, grief, pain, sleep disorders, and cognitive disorders can produce the same changes. With either form, a clinician must decide whether those responses reflect depression, another condition, or both.
Which is more accurate in older adults?
No universal winner has emerged. In a Swedish head-to-head study (2021), 113 community-dwelling adults aged 65 or older completed both questionnaires and a structured diagnostic interview. Seventeen had a major depressive episode. The area under the curve was 0.97 for the GDS-15 and 0.95 for the PHQ-9, and the authors judged the two comparable.
In that sample, a PHQ-9 cutoff of 10 had 71% sensitivity and 95% specificity. The authors suggested that cutoff may be too high for older adults in Sweden. The study is useful but too small and setting-specific to establish one tool as better everywhere.
The USPSTF evidence review (2023) pooled seven GDS-15 studies using a cutoff of 5 or higher. Estimated sensitivity was 0.94 and specificity was 0.81 among 5,655 participants. Results varied greatly across studies, so those figures are not a guarantee for one clinic or patient.
For the PHQ-9, an individual participant data meta-analysis (2021) found 85% sensitivity and 85% specificity at a cutoff of 10 or higher against semistructured interviews. Age effects were small, and the authors did not support a separate lower threshold for all older adults. The evidence therefore supports local protocol selection and clinical follow-up, not a cutoff change based only on age.
When should you choose the GDS-15 or the PHQ-9?
Start with the purpose of the screen and the evidence for the intended setting.
The GDS-15 suits a protocol designed and validated for older adults, or one where reducing somatic symptom content is important. It also suits a validated administration plan that uses a yes-or-no format. It can reduce one source of symptom overlap, but it still cannot show what caused a change. Review the answers and functioning, not just the total.
The PHQ-9 suits a practice that already uses one adult depression workflow, or a care team that needs its symptom profile. It also suits services where consistent adult measurement matters more than minimizing somatic content. Physical symptom responses need context in medically complex patients. The PHQ-9 does not overestimate depression by definition; it records symptoms that may have several explanations.
Self-report alone may not be enough when vision, hearing, language, literacy, fatigue, or cognition affect either questionnaire. Accommodations should preserve the validated wording, response choices, and administration method. If cognitive impairment limits reliable self-report, use a broader clinical assessment and a tool supported for that setting. Do not assume the GDS-15 will solve the problem.
Which cutoff should you use?
A cutoff is not a diagnosis: it identifies a group for closer assessment. GDS-15 guidance differs across sources about whether follow-up begins at 5 or above 5. Keep the convention named in the local protocol, and do not silently switch thresholds when comparing results. The GDS-15 score guide explains the display ranges Survey Doctor uses and their limits.
The PHQ-9 commonly uses 10 or higher as a follow-up threshold in adult screening evidence. Lowering a threshold catches more potential cases but also increases false positives. That tradeoff belongs in a documented protocol with a diagnostic follow-up process, not an improvised age-based rule. See what a PHQ-9 score means for interpretation limits.
Does either questionnaire assess safety?
Neither tool completes a safety assessment. The GDS-15 does not directly ask about suicide or self-harm. The PHQ-9 includes one question about thoughts of death or self-harm.
If you need help now. In the US, Call 988 or text 988. Call 911 if you are in immediate danger. Outside the US, contact your local emergency number or find support in your country.
Follow up directly on any endorsement of PHQ-9 item 9, regardless of the total. Ask about current safety separately when using the GDS-15 or whenever the clinical situation raises concern.
How should you track and compare scores?
There is no evidence-based schedule that fits every older adult. The USPSTF recommendation (2023) found little evidence on the optimal screening interval. Base timing on prior screening, current symptoms, risk factors, comorbidities, major life events, treatment context, and the ability to provide follow-up.
Scores from the GDS-15 and PHQ-9 are not interchangeable, so use the same instrument and protocol unless there is a documented reason to switch. If both are given and the totals disagree, do not guess at the cause. A higher PHQ-9 with a lower GDS-15 does not prove that medical symptoms inflated the PHQ-9. The reverse pattern does not prove a purely psychological cause.
Instead, review the individual answers, recall periods, administration conditions, recent health changes, medications, cognition, and function. Then complete the clinical assessment needed to explain the pattern. Whichever form you choose, document the cutoff and follow-up pathway before screening begins.