Effect of Physical Comorbidities on Risk of Depression in Multiple Sclerosis

Depression in multiple sclerosis (MS) may be due to several factors, including the presence of physical comorbidities. Using the North American Research Committee on Multiple Sclerosis (NARCOMS) Registry, we examined whether individuals with MS and physical comorbidities have an increased risk of depression compared with those without physical comorbidities and whether they are more likely to remain untreated for depression. In 2006, NARCOMS participants reported their physical and mental comorbidities and completed the Center for Epidemiologic Studies Depression Scale (CESD). We defined a CESD score of 21 or higher as indicating probable major depression. Individuals with elevated CESD scores but no diagnosis of depression were considered undiagnosed. Forty-six percent of participants reported a lifetime history of depression. In a multivariable Cox proportional hazards model, reporting any physical comorbidity was associated with an increased risk of being diagnosed with depression (hazard ratio [HR], 2.20; 95% confidence interval [CI], 2.04–2.38) after MS onset and with an increased risk of diagnosed or undiagnosed depression (HR, 2.37; 95% CI, 2.21–2.54). After adjustment for education, participants with any physical comorbidity were more likely to report treatment for depression (odds ratio [OR], 1.67; 95% CI, 1.24–2.23). Patients with MS and physical comorbidities are at increased risk of depression, but they are more likely to be diagnosed and treated than MS patients without other chronic conditions.