Structural Analysis of the German Self-Report Questionnaire for Anxiety and Depression in People With Disorders of Intellectual Development (SAD-IE)

Abstract

Background

Anxiety disorders and depression are among the most common mental disorders in people with disorders of intellectual development (DID). As many symptoms are not directly observable, diagnoses should not be based solely on third-party assessment. The aim of the study was the development and structural analysis of a self-report questionnaire (SAD-IE) for anxiety and depression in people with DID.

Methods

Based on the specific diagnostic criteria of DM-ID-2, a trial version of the SAD-IE with 49 items was constructed in plain language. After contacting N = 233 institutions across all 16 German federal states, N = 286 adults with DID and their proxies were included. The factorial structure of the SAD-IE was analyzed using confirmatory factor analysis for ordinal data (CFA, WLSMV estimation).

Results

The CFA showed that a two-factor model captured the latent structure of the SAD-IE best (CFI = 0.956, TLI = 0.954, RMSEA = 0.040, SRMR = 0.069), with 39 of the original items having sufficient discriminatory power. The first factor, depression, was reliably represented by 22 items (r (it,c) = 0.520–0.770; α = 0.900, ω = 0.901) and the second factor, anxiety, by 17 items (r (it,c) = 0.504–0.796; α = 0.895, ω = 0.897).

Conclusion

The German SAD-IE is a reliable self-report questionnaire measuring the major symptoms of anxiety and depression in people with borderline, mild, or moderate DID. It provides the foundation for an urgently needed self-assessment in addition to existing third-party assessments, ensuring a more comprehensive diagnosis. Further evaluation in practice is recommended.

Summary

• The SAD-IE is a self-report questionnaire in German that can be completed independently or with little assistance by people with borderline or mild to moderate DID. Instructions and items of the SAD-IE are written in plain language, and pictures for augmentative and alternative communication (AAC) are provided.
• The SAD-IE takes into account the deviations in anxiety and depression in people with DID compared to the general population.
• The SAD-IE includes relevant items to diagnose anxiety and depression, as well as two additional items to measure general psychological distress.
• The SAD-IE is designed as a screening tool but could also be used to monitor subjective changes in symptoms during follow-up assessments or in research.