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.
Why the choice matters
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.
Neither questionnaire can determine the cause. Some of the same changes occur with medical illness, medication effects, grief, pain, sleep disorders, and cognitive disorders. Choose the screen that fits the intended population, clinical workflow, and follow-up process.
GDS-15 and PHQ-9 at a glance
| 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. It still includes energy and activity. The PHQ-9 includes sleep, fatigue, appetite, and movement changes. With either form, a clinician must decide whether those responses reflect depression, another condition, or both.
What the evidence shows
No universal winner emerged. In one Swedish study, 113 community-dwelling adults age 65 or older completed both questionnaires and a diagnostic interview. Seventeen had a major depressive episode. The reported area under the curve was 0.97 for the GDS-15 and 0.95 for the PHQ-9. The difference was not statistically significant. Those results from the Swedish head-to-head study (2021) are 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 should not be treated as a guarantee for one clinic or patient.
For the PHQ-9, an individual participant data meta-analysis (2021) found that a cutoff of 10 or higher produced 85% sensitivity and 85% specificity against semistructured interviews. Age effects were small. 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.
How to choose between them
Start with the purpose of the screen and the evidence for the intended setting.
Consider the GDS-15 when
- the protocol was designed and validated for older adults;
- reducing somatic symptom content is important; or
- a yes-or-no response format fits the validated administration plan.
The GDS-15 can reduce one source of symptom overlap, but it does not determine whether a change comes from depression, illness, medication, cognition, or circumstances. Review the answers and functioning, not just the total. Our GDS-15 score guide explains the current display ranges and their limits.
Consider the PHQ-9 when
- the practice already uses one adult depression workflow;
- the care team needs the PHQ-9 symptom profile; or
- consistent measurement across adult services 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. See what a PHQ-9 score means for interpretation limits.
Use more than self-report when needed
Vision, hearing, language, literacy, fatigue, and cognition can 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 rather than assuming the GDS-15 will solve the problem.
Cutoffs are follow-up thresholds
A cutoff is not a diagnosis. It identifies a group for closer assessment. GDS-15 guidance also differs across sources about whether follow-up begins at 5 or above 5, so keep the convention named in the local protocol and do not silently switch thresholds when comparing results.
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.
Safety requires a separate assessment
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.
When the scores disagree
Do not guess at the cause of discordant totals. 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.
How often to screen
There is no evidence-based schedule that fits every older adult. The USPSTF recommendation (2023) found no optimal interval. Base timing on prior screening, current symptoms, risk factors, comorbidities, major life events, treatment context, and the ability to provide follow-up.
Use the same instrument and protocol when tracking change unless there is a documented reason to switch. Scores from the GDS-15 and PHQ-9 are not interchangeable.
Bottom line
Whichever form you choose, document the cutoff and follow-up pathway before screening begins. Review the individual answers and current safety alongside the total.