Anxiety and depression influence the relation between disability status and quality of life in multiple sclerosis

Disability status, depression and anxiety are important determinants of quality of life (QoL) in patients with multiple sclerosis (MS). We investigated whether anxiety and depression influence the relation between disability status and QoL in our cohort of recently diagnosed patients. Disability status [Expanded Disability Status Scale (EDSS)], anxiety and depression [Hospital Anxiety and Depression Scale (HADS)], and QoL (SF-36) were prospectively obtained in 101 MS patients. The relation between EDSS and SF-36 scales was examined using regression analyses, without and with adjustment for anxiety and depression. Interaction effects were investigated by comparing the relation between EDSS and QoL in patients with high and low anxiety and depression. In the unadjusted analyses, EDSS was significantly related to all SF-36 physical and mental health scales. After adjustment for anxiety and depression, EDSS was significantly related only to the SF-36 physical functioning, role-physical functioning and bodily pain scales. The relation between EDSS and these SF-36 scales was consistently higher in patients with more symptoms of anxiety or depression, suggesting that anxiety and depression strengthened the association of EDSS in these SF-36 physical health scales. After adjustment for anxiety and depression, EDSS was not significantly related to the SF-36 mental health scales and the general health scale. This finding is compatible with the hypothesis that anxiety and depression are intermediate factors in the association of EDSS with these SF-36 scales. Screening for symptoms of anxiety and depression is recommended in studies that use QoL as an outcome measure of treatment or intervention efficacy.