Somatoform dissociation among Swedish adolescents and young adults: the psychometric properties of the Swedish versions of the SDQ-20 and SDQ-5.

BACKGROUND Somatoform dissociation is supposed to be a vital aspect of the general concept of dissociation. The Somatoform Dissociation Questionnaire-20 (SDQ-20) and the brief version SDQ-5 are self-report instruments constructed to identify somatic dissociation. AIM In the present study, the psychometric qualities of the Swedish version of the SDQ-20 and its brief version, the SDQ-5, were examined among adolescents and young adults. Reliability and concurrent validity were investigated. METHODS A total of 512 adolescents and young adults participated in the study: 461 adolescents from a non-clinical sample and 50 adolescents and young adults from a clinical eating disorder outpatient unit. They completed the self-report instruments the SDQ-20, the SDQ-5 (part of SDQ-20), the Linköping Youth Life Experience Scale (LYLES, a trauma history scale) and the Dissociation Questionnaire-Sweden (Dis-Q-Sweden). RESULTS Both internal consistency and test-retest reliability of the Swedish version of SDQ-20 were good in both the non-clinical (α = 0.83) and the clinical groups (α = 0.84); the reliability for the SDQ-5 was, however, lower (non-clinical α = 0.50, clinical α = 0.64). Significant differences were found between the clinical and non-clinical groups on both somatoform and psychoform dissociation. Correlations between the Dis-Q-Sweden, SDQ-20 and SDQ-5 were generally high. The criterion and convergent validity was acceptable for both scales but somewhat better for SDQ-20 than for SDQ-5. CONCLUSION The advantage with both the SDQ-20 and the SDQ-5 is that they are short questionnaires, but the results suggests that SDQ-20 is preferable based on the higher-quality psychometric properties of the SDQ-20.