Psychometric Properties of the Nine-Item Personal Health Questionnaire (PHQ-9) Seven-Item Generalised Anxiety Disorder Scale (GAD-7), and the Work and Social Adjustment Scale (WSAS) With People With Intellectual Disabilities.
PHQ-9, GAD-7, and WSAS are psychometrically sound for quick depression, anxiety, and function screening in adults with intellectual disabilities.
01Research in Context
What this study did
Dagnan et al. (2025) checked if three common mental-health forms work for adults with intellectual disabilities. The forms were the PHQ-9 for depression, the GAD-7 for anxiety, and the WSAS for daily-life problems. They ran standard math tests to see if the questions hang together and make sense in this group.
What they found
All three forms held up well. The questions stayed consistent, and the factor pattern looked like it does in the general population. In plain words, the tools appear ready for routine screening.
How this fits with other research
Cheves et al. (2026) extend this work by building a brand-new 27-item distress scale just for adults with ID. Their OWLS-ID backs up Dave’s finding that reliable self-report is possible, but it adds a bespoke option when you want questions written in ID-friendly language.
Older PAS-ADD family studies (H et al. 1998; L et al. 2011; F et al. 2013) already showed mental-health screening can work in ID services. Dave’s team now widens the menu: you can keep using PAS-ADD tools or plug in the shorter PHQ-9/GAD-7/WSAS trio with equal confidence.
No clash appears here—just more choices. The new data do not replace earlier tools; they simply give you faster, public-domain forms that save time and money.
Why it matters
If you serve adults with ID, you can now screen for depression, anxiety, and life-impact without hunting for special forms. The PHQ-9, GAD-7, and WSAS are free, short, and backed by solid numbers. Use them during intake, annual reviews, or when behavior spikes to catch hidden mental-health issues early and refer on time.
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02At a glance
03Original abstract
BACKGROUND: The nine-item Physical Health Questionnaire (PHQ-9), the seven-item Generalised Anxiety Disorder scale (GAD-7) and the Work and Social Adjustment Scale (WSAS) are, respectively, self-report measures of depression, generalised anxiety, and the impact of mental health on the person's personal functioning that are widely used in mainstream mental health services in England. The psychometric properties of these scales when used with people with intellectual disabilities have not been established. METHOD: Item level data for the PHQ-9 (n = 128), GAD-7 (n = 124) and WSAS (n = 133) for people with intellectual disabilities in an English NHS Talking Therapies for anxiety and depression (NHSTT) service in the north of England were analysed using internal reliability statistics and confirmatory factor analysis. RESULTS: In this study, the full PHQ-9, GAD-7 and WSAS have Cronbach's α of 0.81, 0.84 and 0.81, respectively, and have acceptable ranges of corrected item-total correlations. The two-factor structures for the PHQ-9 and the GAD-7 were a better fit than single-factor structures, although the single-factor fit and the correlation between the two factors within each scale suggest that their use as a single scale is justified. The single-factor structure for the WSAS was a good fit. CONCLUSIONS: In this study, the widely used PHQ-9, GAD-7 and WSAS demonstrate internal consistency values and factor analysis structure similar to those for individuals without intellectual disabilities. The data support the use of these measures for people with intellectual disabilities attending routine primary care mental health services.
Journal of intellectual disability research : JIDR, 2025 · doi:10.1111/jir.13231