Being a parent reduces your risk of catching a cold -- possibly because of unknown "psychological or behavioral differences between parents and nonparents," according to a study in the July issue of Psychosomatic Medicine, the official journal of the American Psychosomatic Society.

The risk of becoming ill after exposure to cold viruses is reduced by about half in parents compared to nonparents, regardless of pre-existing immunity, according to research led by Rodlescia S. Sneed, MPH, and Sheldon Cohen, PhD of Carnegie Mellon University, Pittsburgh. The study suggests that other, yet unknown factors related to being a parent may affect susceptibility to illness.

Being a Parent Protects Against Colds

The researchers analyzed data on 795 adults from three previous studies of stress and social factors affecting susceptibility to the common cold. In those studies, healthy volunteers were given nose drops containing cold-causing rhinovirus or influenza viruses.

After virus exposure, about one-third of volunteers developed clinical colds -- typical symptoms of a cold plus confirmed infection with one of the study viruses. The analysis focused on whether being a parent affected the risk of developing a cold, with adjustment for other factors.

The results showed a lower rate of colds among parents, compared to volunteers who were not parents. In the adjusted analysis, the risk of developing a cold was 52 percent lower for parents.

That might be expected on the basis of immunity -- kids get colds, and parents may develop protective antibodies against the specific viruses causing those colds. However, the lower risk of colds in parents could not be explained by pre-existing immunity, based on levels of antibodies to the study viruses. Parents were less likely to develop colds whether or not they had protective levels of antibodies.

The protective effect of parenthood increased along with the number of children (although there were limited data on parents with three or more children). Parents were at reduced risk of colds even when they didn't live with any of their children. In fact, parents with no children at home had an even larger, 73 percent reduction in risk.

The risk of colds was lower for parents in most age groups. The only exception was parents in the youngest age group -- 18 to 23 years -- for whom the risk of colds was no different than for nonparents. There was no difference in the risk of colds for parents who were married versus unmarried.

Psychological or Behavioral Factors May Play a Role

"We found parenthood predicted a decreased probability of colds among healthy individuals exposed to a cold virus," Sneed and coauthors write. The effect is independent of parental immunity, suggesting that psychological or behavioral factors could be involved.

However, the study permits no conclusions as to what those protective factors might be. One possibility is that being a parent improves regulation of immune factors (cytokines) triggered in response to infection. Previous studies have shown that cytokine responses explain the protective effects of psychological factors -- such as lower stress or a positive attitude -- against cold risk.

But more research will be needed to clarify just how being a parent could affect the body's response to cold viruses. Sneed and colleagues conclude, "Our results, while provocative, have left room for future studies to pursue how various aspects of parenthood (eg, frequency of contact with children, quality of parent/child relationships) might be related to physical health, and how parenthood could 'get under the skin' to influence physical health."