The study by University of Wisconsin-Madison researchers and their colleagues found that people who experience chronic marital stress are less able to savour positive experiences, a hallmark of depression.
They are also more likely to report other depressive symptoms, according to study leader Richard Davidson, UW-Madison William James and Vilas Professor of Psychology and Psychiatry.
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, researchers said.
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 criticised 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, 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 muscle, was measured to assess the intensity and duration of their response.
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.
Prior studies have shown that depressed individuals have a fleeting response following positive emotional triggers.
Davidson was interested in not just how much a muscle relaxes or tenses when a person looks at an image but also in how long it takes the response to subside.
Study participants who reported higher marital stress had shorter-lived responses to positive images than those reporting more satisfaction in their unions. There was no significant difference in the timing of negative responses.
The study was published in the Journal of Psychophysiology.