Psychiatric comorbidity is common in patients with multiple sclerosis (MS), and affects the MS community more frequently than a matched control population, although the incidence is stable over time, according to recent findings of a study published in the journal Neurology, the Official Journal of the American Academy of Neurology. In the study, researchers also reported that compared to women, men face a disproportionately greater relative burden of depression when they develop MS.

Depression and anxiety reduce the quality of life in patients with MS, and depression has been found to be associated with reduced persistence to disease-modifying therapy. While such adverse effects of psychiatric comorbidity are recognized in MS patients, its epidemiology remains poorly investigated.

With the goal of comparing the prevalence and incidence of psychiatric comorbidity in patients with MS to age, sex, and geographic area matched controls, in the study entitled “Differences in the burden of psychiatric comorbidity in MS vs the general population,” Ruth Ann Marrie, MD, PhD, and colleagues used data from four Canadian provinces and identified 44,452 MS patients and 220,849 matched controls. The team investigated the prevalence and incidence of bipolar disorder, anxiety, depression, and schizophrenia between 1995 and 2005.

The results revealed that in 2005, the annual incidence of depression per 100,000 patients with MS was 979, while the incidence of bipolar disorder was 328, anxiety was 638, and for schizophrenia the incidence was 60 cases. The results also showed that the prevalence and incidence estimates of all psychiatric conditions were higher in the group of patients with MS when compared to the matched controls.

Although the incidence of depression was found to be higher in women compared to men in both groups, the difference in the incidence rates between the sexes was found to be lower in the group of patients with MS compared to the matched control group. Incidence rates were found to be constant over time while prevalence was found to be slightly increased.

According to the research team, these results indicate that there may exist a nonspecific effect of MS on psychiatric comorbidity, as MS was found to increase the risk of all psychiatric conditions analyzed, which implies the need for general psychiatric support rather than only illness-specific strategies.

“While the incidence and prevalence of these conditions changed little over 10 years, their increased frequency in the MS population as compared to the matched population indicates the increased burden these conditions impose on the MS population. While women with MS face a particularly high risk of depression and anxiety, men with MS face a disproportionately greater increase in the risk of depression when they develop MS,” concluded the research team in their article.