Environmental risk factors and multiple sclerosis: an umbrella review of systematic reviews and meta-analyses

The cause of multiple sclerosis is believed to involve environmental exposure and genetic susceptibility. We aimed to summarise the environmental risk factors that have been studied in relation to onset of multiple sclerosis, assess whether there is evidence for diverse biases in this literature, and identify risk factors without evidence of biases.We searched PubMed from inception to Nov 22, 2014, to identify systematic reviews and...