Biomarkers and depression in Multiple Sclerosis : a longitudinal pilot study

Depression is the most common psychiatric symptom experienced by people with multiple sclerosis (pwMS). Pathological inflammation, a characteristic hallmark of multiple sclerosis, has shown to alter peripheral and brain biomarkers implicated in the development and perpetuation of depression. However, few studies have examined this relationship in pwMS. The first study cross-sectionally examined the relationship between inflammatory biomarkers and depression in pwMS compared to healthy participants. The results suggested: (1) pwMS have higher levels of depressive symptoms than healthy participants; (2) proinflammatory cytokines do not differ across pwMS and healthy participants; and (3) some kynurenine-pathway metabolites differ and are involved in depression in pwMS. The second study examined the relationship between inflammatory biomarkers and depression in pwMS cross-sectionally and longitudinally (5-to-6-year period). The results suggested: (1) there are moderate cross-sectional relationships between some proinflammatory cytokines and kynurenine-pathway metabolites in pwMS at baseline; (2) some proinflammatory cytokines increase in pwMS overtime; and (3) no detected relationships between proinflammatory cytokines and depression in pwMS. The contribution of these findings toward the current understanding of inflammatory biomarkers in the pathogenesis and treatment of depression in pwMS is discussed. Future studies examining the role of biomarkers in depression in pwMS are required.