Abstract
Background. Individuals with long-term physical health conditions (LTCs) experience higher rates of depression and anxiety. Conventional self-report measures do not distinguish distress related to LTCs from primary mental health disorders. This difference is important as treatment protocols differ. We developed a transdiagnostic self-report measure of illness-related distress, applicable across LTCs.
Methods. The new Illness-Related Distress (IRD) scale was developed through thematic coding of interviews, systematic literature review, think-aloud interviews with patients and healthcare providers and expert-consensus meetings. An internet sample (n=1398) of UK-based individuals with LTCs completed the IRD scale for psychometric analysis. We randomly split the sample (1:1) to conduct: 1) an exploratory factor analysis (EFA; n= 698) for item reduction, and 2) iterative confirmatory factor analysis (CFA; n=700) and exploratory structural equation modelling (ESEM). Here, further item reduction took place to generate a final version. Measurement invariance, internal consistency, convergent, and test-re-test reliability, and clinical cut-points were assessed.
Results. EFA suggested a 2-factor structure for the IRD scale, subsequently confirmed by iteratively comparing unidimensional, lower order, and bifactor CFAs and ESEMs. A lower order correlated 2-factor CFA model (two 7-item subscales: intrapersonal distress and interpersonal distress) was favoured and was structurally invariant for gender. Subscales demonstrated excellent internal consistency, very good test-retest reliability, and good convergent validity. Clinical cut points were identified (intrapersonal=15, interpersonal= 12).
Conclusion. The IRD scale is the first measure that captures transdiagnostic distress. It may aid assessment within clinical practice and research related to psychological adjustment and distress in LTCs.
Methods. The new Illness-Related Distress (IRD) scale was developed through thematic coding of interviews, systematic literature review, think-aloud interviews with patients and healthcare providers and expert-consensus meetings. An internet sample (n=1398) of UK-based individuals with LTCs completed the IRD scale for psychometric analysis. We randomly split the sample (1:1) to conduct: 1) an exploratory factor analysis (EFA; n= 698) for item reduction, and 2) iterative confirmatory factor analysis (CFA; n=700) and exploratory structural equation modelling (ESEM). Here, further item reduction took place to generate a final version. Measurement invariance, internal consistency, convergent, and test-re-test reliability, and clinical cut-points were assessed.
Results. EFA suggested a 2-factor structure for the IRD scale, subsequently confirmed by iteratively comparing unidimensional, lower order, and bifactor CFAs and ESEMs. A lower order correlated 2-factor CFA model (two 7-item subscales: intrapersonal distress and interpersonal distress) was favoured and was structurally invariant for gender. Subscales demonstrated excellent internal consistency, very good test-retest reliability, and good convergent validity. Clinical cut points were identified (intrapersonal=15, interpersonal= 12).
Conclusion. The IRD scale is the first measure that captures transdiagnostic distress. It may aid assessment within clinical practice and research related to psychological adjustment and distress in LTCs.
| Original language | English |
|---|---|
| Journal | Psychological Medicine |
| Publication status | Accepted/In press - 24 Mar 2025 |