Development and psychometric properties of the Glasgow Depression Scale for people with a learning disability: Individual and carer supplement versions

Abstract

Background: There is no reliable and valid self-report measure of depressive symptoms for people with learning disabilities. Aims: To develop a scale for individuals with learning disability, and a supplementary scale for carers. Method: Items were generated from a range of assessment scales and through focus groups. A draft scale was piloted and field tested using matched groups of people with or without depression, and their carers. The scale was also administered to a group without learning disabilities for criterion validation. Results: The Glasgow Depression Scale for people with a Learning Disability (GDS-LD) differentiated depression and non-depression groups, correlated with the Beck Depression Inventory - II (r=0.88), had good test-retest reliability (r=0.97) and internal consistency (Cronbach's α=0.90), and a cut-off score (13) yielded 96% sensitivity and 90% specificity. The Carer Supplement was also reliable (r=0.98; α=0.88), correlating with the GDS- LD (r=0.93). Conclusions: Both scales appear useful for screening, monitoring progress and contributing to outcome appraisal.