Childhood adversity, allostatic load and epigenetic signatures in paediatric and adult-onset multiple sclerosis.

Childhood adversity is increasingly recognized as a critical modifier of neurologic disorder development and disease severity, including in the neuroimmune disorder multiple sclerosis (MS). While previous studies have linked early-life adversity to increased MS susceptibility and more severe disease, the underlying biological mechanisms remain poorly understood. This study investigated associations between childhood adversity and MS clinical features, with a focus on two potential pathogenic mechanisms: allostatic load and epigenetic modifications. We evaluated 60 consecutively enrolled young adults with MS; 30 with paediatric-onset MS (POMS) and 30 with adult-onset MS (AOMS). At time of enrolment in this cross-sectional study, participants had MS disease duration of 6 years on average. POMS participants were mean 22.09 (2.66) years and AOMS participants were mean 32.41 (2.19) years old. 62% of participants were female. Childhood adversity was defined using a composite index of individual, family and socioeconomic measures captured by the adverse childhood experiences questionnaire, parental education level and estimated household income during childhood. Clinical outcomes included patient-reported SymptoMScreen questionnaire regarding MS symptom burden and MS neurologist-assessed disability using the Expanded Disability Status Scale (EDSS) of the participant's neurologic exam at the time of enrolment. Circulating biomarkers of allostatic load and genome-wide epigenetic profiles (DNA methylation via RRBS; reduced representation bisulfite sequencing) were also assessed. A history of high childhood adversity was associated with significantly greater patient-reported MS symptom burden (P = 0.001) and higher neurologist-reported EDSS disability scores (P = 0.028), independent of disease duration or timing of treatment initiation. There were no differences between childhood adversity and circulating biomarkers of allostatic load. While childhood adversity was not associated with global epigenetic changes across the entire cohort, stratified analysis revealed divergent methylation patterns by age of MS onset: POMS participants with childhood adversity had increased DNA methylation, whereas AOMS participants with childhood adversity showed decreased methylation compared to individuals without childhood adversity. None of the observed clinical and biologic differences were explained by differences in disease duration or the interval between symptom onset and treatment initiation. Our findings suggest that childhood adversity is associated with increased MS symptom burden and neurologic disability in young adults with MS. Childhood adversity may differentially shape the epigenome, depending on the age of MS onset, with potential implications for disease trajectory and therapeutic vulnerability. These results support the biological embedding of childhood adversity in MS and highlight the need for age- and exposure-sensitive approaches to understanding MS pathogenesis across the lifespan.