Think twice before having a spat with your spouse, especially if one of you is injured.
The stress from even a 30-minute argument can increase healing time by up to one day, according to a recent study published in the Archives of General Psychiatry.
The research is important because it explains a mechanism through which this can occur, said Cinnamon Stetler, a psychology researcher at the University of British Columbia. It is "bringing the real world of marriage into the lab," said Stetler, who was not involved in the research.
Marital studies have been continuing since the 1980s at Ohio State University's Institute for Behavioral Medicine Research.
They have found that more hostile couples have a greater production of stress hormones, said Janice Kiecolt-Glaser, the lead researcher at Ohio State and a professor of psychology and psychiatry.
She has been studying wound healing since the 1990s and found that here was a clear effect of stress.
Kiecolt-Glaser is combining the two studies and examining how marital stress affects wound healing.
The researchers selected a group of 42 married couples who met strict health requirements. At the institute, the couples made two 24-hour visits that were two months apart.
At the start and end of each visit, the participants gave blood to measure systemic levels of pro-inflammatory cytokines, which are proteins important to healing and inflammation.
Local cytokine production is good for healing, whereas systemic circulation of cytokines is not good news, Kiecolt-Glaser said. This is because cytokines increase inflammation, which is linked to ailments such as heart disease and arthritis.
For the wound-healing part of the study, the researchers applied a suction device that created eight pea-sized blisters on each participant's forearm. The blister wounds were superficial.
"It is just like you had a blister yourself," Kiecolt-Glaser said.
A chamber covered the blisters to collect the person's serum, which was used to measure cytokine levels. After removing the chamber, they assessed the blister wounds daily for eight days and again on day 12.
They measured wound temperature and humidity, keys to healing.
To study marital stress, husbands and wives individually completed questionnaires on their marriage.
Then during the first visit, the couples were directed to focus on positive and supportive interactions. Each husband or wife was asked to talk for 10 minutes about something they would like to change about themselves, with the condition that it couldn't relate to the marriage itself. People commonly talked about being more organized and losing weight, Kiecolt-Glaser said.
At the second visit, the researchers used the questionnaire information to get the couples to argue for 30 minutes.
Common themes were finances, in-laws, free time and children, Kiecolt-Glaser said.
The researchers taped both the supportive and argumentative interactions and used the Rapid Marital Interaction Coding system to distinguish between the distressed and non-distressed couples.
To study people in a situation where their interactions can be objectively classified is a major strength of the research, said Kenneth Freedland, a professor of psychiatry at Washington University in St. Louis. Freedland was not involved in the research.
The results show that "stress is more important than we thought," Kiecolt-Glaser said.
After argumentative interactions, blister wounds healed more slowly than after supportive interactions. The local level of cytokines, which promote healing, was also lower. Couples with high baseline hostility had higher circulating levels of cytokines in their bodies the morning after an argument than couples with low baseline hostility.
Marital discord is a major stress in people's lives. The results are not surprising, said Steven Weisman, the medical director of pain management at Children's Hospital of Wisconsin.
However, there may be other factors that account for differences in cytokine levels. The next step for the researchers should be to look at wound healing in couples before and after marital therapy, said Weisman, who is also a professor of anesthesiology at the Medical College of Wisconsin.
"I don't think people should take away from this that conflict in marriage is bad," Stetler said.
Weisman said stress helps us to survive. Researchers agree that it is chronic stress that may damage the body. The stress in this study was minor.
"Wound healing is a nice way to study stress, because it is an actual challenge to the body," said Suzanne Segerstrom, an associate professor of psychology at the University of Kentucky who was not involved in the research.
The study is a promising lab-based proxy for how someone might recover after surgery, Stetler said.
In this study, the wounds are trivial, Kiecolt-Glaser said. Surgical wounds take much longer to heal. It is possible that stress could have implications for the healing of larger wounds. However, there are still "more pieces of the puzzle to understand," said Carlyle Chan, a professor of psychiatry and behavioral medicine at the Medical College of Wisconsin.
For future research, Kiecolt-Glaser plans to focus on the interaction between stress and inflammation.
She is also interested in whether yoga could help to mediate the effects of the pro-inflammatory cytokines.