Previous research has shown that babies born in the spring have a higher chance of developing multiple sclerosis, a debilitating disease most often diagnosed in young people, and which is especially common in Canada. It has also been documented that MS patients in Europe often carry the HLA-DRB1*15 gene allele. Now, a study of MS patients in Canada, Sweden and Norway has found a link between this gene allele and the seasonal effect. It identified that the HLA-DRB1*15 allele is more common among MS patients born in the spring. The researchers say they aren’t sure how exactly genes interact with the environment, but they suspect that a lack of vitamin D in pregnant mothers may increase the chance of a baby born in the spring developing MS. They hope that this finding will lead to preventative and therapeutic treatments to mitigate a baby’s risk of MS, and to further understanding the relationship between genetics and the environment.