Marital stress may make people more vulnerable to depression, according to a recent study by University of Wisconsin-Madison researchers and their colleagues. The long-term study, published in the April 2014 Journal of Psychophysiology, shows that people who experience chronic marital stress are less able to savor positive experiences, a hallmark of depression. They are also more likely to report other depressive symptoms.

The findings are important, says study leader Richard Davidson, UW-Madison William James and Vilas Professor of Psychology and Psychiatry, because they could help researchers understand what makes some people more vulnerable to mental and emotional health challenges.

It might also help scientists develop tools to prevent them.

"This is not an obvious consequence, if you will, of marital stress, but it's one I think is extraordinarily important because of the cascade of changes that may be associated," says Davidson, founder of the Center for Investigating Healthy Minds at the UW's Waisman Center. "This is the signature of an emotional style that reveals vulnerability to depression."

Married people are, in general, happier and healthier than single people, according to numerous studies. But marriage can also be one of the most significant sources of long-lasting social stress. It's not all wedded bliss.

The researchers thought chronic marital stress could provide a good model for how other common daily stressors may lead to depression and similar conditions.

"How is it that a stressor gets under your skin and how does that make some more vulnerable to maladaptive（不适应的） responses?" says UW-Madison graduate student Regina Lapate. She is the paper's lead author.

For the longitudinal study -- part of the National Institute on Aging-funded Midlife in the United States (MIDUS) study directed by Carol Ryff, director of the Institute on Aging at UW-Madison -- researchers recruited married adult participants to complete questionnaires rating their stress on a six-point scale.

They were asked questions like how often they felt let down by their partner or how frequently their spouse criticized them. They were also evaluated for depression.

Roughly nine years later, the questionnaire and depression assessments were repeated.

In year 11, the participants were invited to the laboratory to undergo emotional response testing, a means of measuring their resilience. Resilience（恢复力）, from an emotional perspective, reflects how quickly a person can recover from a negative experience.

The participants were shown 90 images, a mix of negative, neutral and positive photographs such as a smiling mother-daughter pair. The electrical activity of the corrugator supercilii, also known as the frowning（皱眉头） muscle, was measured to assess the intensity and duration of their response.

As the nickname suggests, the frowning muscle activates more strongly during a negative response. At rest, the muscle has a basal level of tension but during a positive emotional response, the muscle becomes more relaxed.