New study finds partner's happiness linked to lower stress hormone levels in older couples

When comparing individuals' self-reported emotional states and relationship satisfaction with their levels of cortisol, researchersobserved that older couples have lower levels of the stress hormone when their partners feel positive emotions. This effect was even stronger for people who reported higher satisfaction in their relationships. The study was published in September in the journal Psychoneuroendocrinology.

"Having positive emotions with your relationship partner can act as like a social resource," said Tomiko Yoneda, an assistant professor of psychology in the College of Letters and Science and the study's lead author.

The stress hormone and healthy aging

Cortisol is an important part of our bodies' stress response and everyday function. Cortisol increases steeply when we wake up and then tends to decline gradually throughout the day. In acute stress, cortisol spikes, driving our bodies to produce the glucose and higher metabolism we might need for sudden action.

How we feel throughout the day affects our cortisol production. Studies have consistently found that negative emotions are linked to higher levels of cortisol, and chronically high levels of cortisol can lead to overall poorer health.

In old age, these links between our emotions and cortisol may be even stronger. Older adults also tend to have stronger physiological responses to stress, but their bodies are less able to slow down their cortisol production. For older couples, intimate relationships might play a role in managing their cortisol levels, researchers said.

"Positive emotions can buffer the production of cortisol," said Yoneda. "This is especially relevant when we think about how our relationship partners might actually bolster that effect."

Connecting happiness and cortisol in older couples

Yoneda and her research team analyzed data from 321 adults from 56 to 87 years of age across three intensive studies in Canada and Germany between 2012 and 2018. The analysis compared people's self-reported emotional states and their relationship satisfaction with levels of cortisol measured by saliva samples. In all three studies, people's emotional states and cortisol were measured multiple times each day for a full week.

The study found that a person's body produced less cortisol in moments when their partner reported higher positive emotions than usual. This effect was even stronger than when people reported their own positive emotions. It was also stronger among those who were older and people who reported being happier in their relationship.

The study didn't find any links between a person's cortisol levels and their partner's negative emotions. Yoneda said this is not surprising, as prior research suggests that older adults may shield their partners from a physiological response to negative emotions in others.

Building both happiness and health for life

Yoneda said that these results are also consistent with a psychological theory that suggests positive emotions increase our ability to act more fluidly in the moment. These experiences can create a positive feedback loop that enhances this ability over time.

The study suggests that people in relationships can share these benefits when they experience positive emotions.

"Relationships provide an ideal source of support, especially when those are high-quality relationships," said Yoneda. "These dynamics may be particularly important in older adulthood."

This research was completed in collaboration with Theresa Pauly, Simon Fraser University; Christiane Hoppmann, University of British Columbia; and researchers from Humboldt Universität Berlin, Berlin, Germany, and Stanford University.