An evaluation of the psychometric properties of the adapted PHQ-9 and GAD-7 outcome measures for use with adults with intellectual disability.

BackgroundPeople with intellectual disability often face barriers accessing mainstream psychological services due to a lack of reasonable adjustments, including the absence of adapted versions of routine outcome measures. Adapted versions of the Patient Health Questionnaire-9 (PHQ-9) and the Generalised Anxiety Disorder-7 (GAD-7) have been created for adults with ID.AimsThis study aims to evaluate the psychometric properties of the adapted PHQ-9 and GAD-7.MethodThe adapted PHQ-9 and GAD-7 and the Glasgow Depression and Anxiety Scales (GDS-ID, GAS-ID) were administered to 47 adults (n=21 clinical group; n=26 community group) with ID. Cross-sectional design and between-group analyses tested for discriminant validity. Concurrent and divergent validity was tested using correlational designs. Reliability was investigated by internal consistency and test-retest analysis.ResultsThe clinical group scored significantly higher on the adapted PHQ-9 (t₄₅=-2.28, p=.03, 95% CI [-7.09, -.45]) and GAD-7 (t₄₅=-3.52, p=.001, 95% CI [-7.44, -2.02]) than the community group, evidencing discriminant validity. The adapted PHQ-9 correlated with the GDS-ID (r₄₇=.86, p