Introduction and objective:
Multiple sclerosis (MS) is a chronic, inflammatory, demyelinating disease of the central nervous system (CNS) involving immune-mediated damage to myelin and axons. Its etiology is not fully understood, but both genetic susceptibility and environmental factors contribute to disease risk. The aim of the review is to summarize current knowledge on the most relevant environmental risk factors associated with MS

Review methods:
This review is mainly based on meta-analyses and original studies identified in PubMed and Google Scholar database using key words such as ‘multiple sclerosis’, ‘risk factors’, ‘environmental’, and ‘pathogenesis’, published between 2020 – 2025. Relevant studies investigating environmental determinants of MS were selected and analyzed.

Brief description of the state of knowledge:
Prior infection with Epstein-Barr virus (EBV) shows the strongest association with MS (odds ratio [OR] ~3.3). Other established risk factors include vitamin D deficiency, tobacco smoking (OR ~1.6), and obesity (OR ~1.2). These factors may contribute to MS development through immune dysregulation, chronic inflammation, and neurotoxic effects. Exposure during critical developmental periods, particularly childhood and adolescence, appears to be especially important. Additional factors, such as psychological stress and other viral infections, have been suggested, but current evidence remains limited.

Summary:
Environmental factors play a significant role in MS pathogenesis, likely through cumulative and interacting effects. A better understanding of these factors may support the development of preventive strategies in the future and improve early risk assessment.