Background: The assessment of mental distress is a central aspect in pain research and treatment. Particularly for depression the comorbidity with pain poses methodological and conceptual challenges. This study examined the psychometric properties of the short version of the depression, anxiety and stress scale (DASS), used in both pain research and treatment and constructed to overcome the particular problems by omitting somatic items and concentrating on the psychological core aspects of depression, anxiety and stress.
Method: The psychometric properties of the DASS-21 were compared between patients with pain and various people without any pain problems (N = 950). The DASS has three subscales, depression, anxiety and stress, each with seven items. The construct validity of the DASS was examined using the hospital anxiety and depression scale (HADS) for anxiety and depression and the general depression scale (Allgemeine Depressionsskala, ADS) for depression. The sensitivity and specificity for depression were determined against a structured interview for diagnostic and statistical manual of mental disorders (DSM-IV) and compared with the Center for Epidemiological Studies depression scale (CESD) and HADS in pain patients.
Results: Cronbach's alpha of the DASS for the depression subscale was at least 0.91, while the anxiety and stress subscales had Cronbach alphas of 0.78-0.82 and 0.81-0.89, respectively. Although the depression subscale has only 7 items, it is just as reliable as the ADS with 21 items. It also has a better sensitivity and specificity than the HADS in identifying clinical patients with depression.
Discussion: The DASS is a reliable questionnaire, free to use and brief to administer; therefore, it is an alternative to the previously used instruments for the screening of depression. Furthermore, the subscale stress measures irritability and tension, which are important aspects of pain experience but underused in assessment procedures for the diagnosis and treatment evaluation of patients with pain.
Keywords: Mental stress; Pain; Questionnaire; Sensitivity; Specificity.