Parenthood influences health in a positive way, a new study has found.

New research led by Carnegie Mellon University's (CMU) Sheldon Cohen and Rodlescia S. Sneed provides the first evidence that, when exposed to a common cold virus, parents are 52 per cent less likely to develop a cold than non-parents.

"We have had a long-term interest in how various social relationships influence health outcomes," said Cohen, the Robert E. Doherty Professor of Psychology within CMU's Dietrich College of Humanities and Social Sciences.

"Parenthood was especially interesting to us because it has been proposed that it can have both positive and negative effects on health. For example, being a parent can be stressful but at the same time can be fulfilling, facilitate the development of a social network and provide purpose in life," Cohen said.

For the study, Cohen, Sneed, Ronald B. Turner of the University of Virginia Health Center and William J. Doyle of the University of Pittsburgh School of Medicine exposed 795 healthy adults between the ages of 18 and 55 to a virus that causes common cold.

Participants reported their parenthood status, and analyses were controlled for immunity to the experimental virus, viral strain, season, age, sex, race, ethnicity, marital status, body mass, employment status and education.

Parents with one or two children were 48 percent less likely to get sick while parents with three or more children were 61 percent less likely to develop a cold.

Both parents with children living at home and away from home showed a decreased risk of catching a cold. And, while parents older than age 24 were protected from the cold virus, parenthood did not influence whether those aged 18-24 became ill.

"Although parenthood was clearly protective, we were unable to identify an explanation for this association," Cohen said.

"Because we controlled for immunity to the virus, we know that these differences did not occur just because the parents were more likely to have been exposed to the virus through their children. Moreover, parents and nonparents showed few psychological or biological differences, and those that did exist could not explain the benefit of parenthood. We expect that a psychological benefit of parenthood that we did not measure may have been responsible," Cohen added.

The research was published in Psychosomatic Medicine.