A new study finds that stress does not appear to increase a person's risk of developing multiple sclerosis (MS). 

Researchers studied two groups of women nurses from the Nurses' Health Study. The first group of 121,700 nurses between the ages of 30 and 55 were followed starting in 1976. The second group of 116,671 nurses between the ages of 25 and 42 were followed from 1989. Participants were asked to report general stress at home and at work, including physical and sexual abuse in childhood and as teenagers. Of the first group, 77 people developed MS by 2005.

In the second group, 292 people developed the disease by 2004. "The risk of MS is particularly high among young women, and the difference in the number of cases is consistent with the different ages of women in the two groups at the beginning of the MS follow-up," said study author Trond Riise, PhD, with the University of Bergen in Bergen, Norway.

After considering factors such as age, ethnicity, latitude of birth, body mass at age 18 and smoking, the study found that severe stress at home did not increase the risk of developing MS. There was also no significant increased risk in developing MS among those who reported severe physical or sexual abuse during childhood or adolescence.

"While we've known that stressful life events have been shown to increase the risk of MS episodes, we weren't certain whether these stressors could actually lead to developing the disease itself," said Riise. 

"This rules out stress as a major risk factor for MS. Future research can now focus on repeated and more fine-tuned measures of stress," said Riise, who conducted the research as a visiting scholar at the Harvard School of Public Health.

The research is published in the May 31, 2011, print issue of Neurology®.