A study of birth order and multiple sclerosis in multiplex families.
Gaudet JP., Hashimoto L., Sadovnick AD., Ebers GC.
Birth order position for affected siblings was examined for 88 sibships having 2 or more cases of multiple sclerosis (MS). The data show that MS patients are randomly ordered by birth within these multiplex sibships. The data therefore do not support the hypothesis that MS occurs in siblings because of a common environmental exposure as defined by proximity in birth order position.