Sentence completion test for depression (SCD): an idiographic measure of depressive thinking

This study set out to investigate the reliability and validity of the Sentence Completion Test for Depression (SCD) as a clinical measure. In contrast to questionnaire measures of depressive thinking, respondents finish incomplete sentences using their own words. This elicits idiographic information concurrent with measuring depressive thinking.

In Study 1, measures of negative thinking were tested between a depressed group and a non-depressed control group. A preliminary item analysis was conducted and replicated on separate samples in Study 2. Psychometric properties of the test were investigated. In Study 3, idiographic validity and sensitivity to change were explored in a sample of clinical cases with reference to cognitive-behavioural case-formulation.

In Study 1, the depressed group produced more negatives and fewer positives, and the SCD demonstrated good content validity, internal consistency and inter-rater reliability. The preliminary short-form had comparable psychometric properties, and these were replicated on new samples in Study 2. Sensitivity and specificity values were above 90% in both studies. In Study 3, idiographic content generated hypotheses about target problems and dysfunctional beliefs within cognitive-behavioural case-formulation, and SCD scores were sensitive to clinical change.

The SCD demonstrates good construct validity, internal consistency, inter-rater reliability, sensitivity, and specificity. It offers an idiographic assessment of depression that is complementary to questionnaire measures, particularly by generating hypotheses about target problems and dysfunctional beliefs within a cognitive-behavioural case-formulation. This is achieved without loss to reliability and validity at the nomothetic level.