The SDS-C was found to be a valid and reliable instrument for current depressive disorder patients in Taiwan.

Maladaptive sleep-related cognitions and behaviors have been recognized as important etiological factors for primary insomnia. The contribution of these factors in insomnia comorbid with mood disturbances, however, is controversial. This study compared sleep-related beliefs and sleep hygiene practices among primary insomnia and insomnia comorbid with depression and/or anxiety. A total of 292 participants, including 97 good sleepers (GS), 73 primary insomnia patients (PI), 17 insomnia patients with anxiety (AI), 39 insomnia patients with depression (DI), and 66 insomnia patients with anxiety and depression (ADI) were included in the study. All participants went through a clinical interview and completed a package of questionnaires, including the Beck Depression Inventory (BDI) and the Beck Anxiety Inventory (BAI) to assess anxiety and depression levels, as well as the Dysfunctional Belief and Attitude about Sleep Scale (DBAS) and the Sleep Hygiene Practice Scale (SHPS) to assess sleep-related cognitions and sleep hygiene practices. The results showed that there were no significant differences between PI group and the groups with comorbid mood disturbances on the DBAS and the SHPS scores, even with control of the influences of mood symptoms. The results suggest that patients with comorbid insomnia have similar dysfunctional sleep beliefs and maladaptive sleep hygiene practices as in those with primary insomnia. Sleep related cognition and behavior also play an important role in the pathology of comorbid insomnia. In addition to their mood symptoms, interventions targeting these factors might be helpful to alleviate the insomnia in comorbid populations.