The relationship between stress and disease onset and relapse in multiple sclerosis: A systematic review

Background: The impact of stress in persons with multiple sclerosis (MS) is an area of ongoing inquiry. A limited number of published systematic reviews have reported an association between stress and MS onset. In addition to reviewing more recently published evidence, this review expands upon existing systematic reviews by consid-ering the timing of stress exposure (childhood or adulthood).Methods: A review of human-subjects literature published in English after 2010 was conducted between April 2020 and May 2020. In total, 6 databases were searched using the terms 'allostatic load', 'multiple sclerosis (MS)', 'chronic stress', and 'stress', and 13 relevant studies were analyzed. Each article was read by at least two of the authors to confirm its relevance. Studies were categorized based on the timing of stress exposure (childhood or adulthood). Study designs included longitudinal cohort, cross-sectional cohort, cross-sectional case-control, and longitudinal case-control studies. The NIH study quality assessment tools and Strengthening The Reporting of OBservational studies in Epidemiology (STROBE) checklist were used to assess study quality. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines for systematic reviews were followed.Results: Manuscripts reviewed included 8 studies on MS onset, 2 studies on MS relapse, and 3 studies on MS onset and relapse. In total, 5 studies examined childhood stress, 7 studies examined adulthood stress, and 1 study examined both childhood and adulthood stress in 2 respective cohorts. Studies of varying design consistently reported an association between MS relapse and stress, regardless of the timing of stress exposure. However, the link between stress and MS onset was conflicting for both childhood and adult stress exposures.Conclusions: This systematic review is the first to report the strong association between stress and MS relapse, and, contradictory to past reports, an inconsistent relationship between stress and MS onset. Notably, the timing of stress (childhood or adulthood) seems to have little effect on the occurrence of either MS onset or relapse, though no study examined both childhood and adult stress within the same participant. Most studies were conducted in small, homogeneous samples using self-reported stress measures, which ultimately limits the generalizability of the findings. Overall, the state of the science remains tentative for all areas examined in this review, necessitating future research.