The Effects of Dysthymic Disorder on Health-Related Quality of Life and Disability Days in Persons with Comorbid Medical Conditions in the General Population

Abstract

Background: We aimed to investigate in medical disorders the effects of comorbid dysthymic disorder as compared to major depressive disorder (MDD) on health-related quality of life (HR-QoL) and disability days in the general population. Methods: In a population-based study 4,181 individuals were assessed for the presence of dysthymic disorder and depression, utilizing the Composite International Diagnostic Interview. Each participant received a thorough medical examination to assess the presence of comorbid somatic conditions. HR-QoL was evaluated using the Medical Outcomes Survey Short-Form 36 (SF-36) and disability days were provided by self-report. Descriptive statistics, analysis of variance and multivariable logistic regression were used. Results: Comorbidity with illnesses from a maximum of 6 somatic disease groups was more prevalent in persons with dysthymic disorder (78.7%) than in those with MDD (70.4%). Persons with dysthymic disorder had a significantly lower mental health summary score in the SF-36 and more disability days than those with MDD. The physical health summary scores were not significantly different between participants with dysthymic disorder and MDD (after Bonferroni correction), suggesting that limitations in physical functioning due to comorbid medical conditions were similar in both affective disorder groups. Conclusions: These results show that affective disorders comorbid with medical, somatic illnesses have a major impact on HR-QoL and disability with more pronounced effects in dysthymic disorder than in MDD. Differences in the time course of both conditions might contribute to this finding. Our results support the need for an improved identification and treatment of affective disorders in patients with somatic illnesses.