Partner’s positive mood linked to reduced cortisol levels in older couples

A new study published in the journal Psychoneuroendocrinology highlights the profound impact a partner’s positive emotions can have on stress management, particularly in older couples. The findings suggest that when a relationship partner experiences more positive emotions, their partner tends to have lower cortisol levels—a key stress hormone—both moment-to-moment and throughout the day. The connection between a partner’s positivity and cortisol was especially strong in couples with higher relationship satisfaction and among older participants.

The study was motivated by a growing body of evidence linking emotional experiences within intimate relationships to health outcomes. Cortisol, a hormone central to the body’s stress response, fluctuates with emotional states and, when dysregulated, is associated with adverse health conditions such as heightened stress, depression, and chronic illnesses. Older adulthood presents unique challenges, as individuals often exhibit stronger physiological responses to stress and a reduced capacity to regulate cortisol levels effectively.

Recognizing the vital role relationships play in emotional and physical well-being later in life, the researchers sought to understand how a partner’s emotional experiences might influence physiological stress markers like cortisol. Barbara Fredrickson’s Positivity Resonance Theory, which emphasizes that shared positive emotional experiences characterized by mutual care and synchrony enhance well-being and strengthen bonds, inspired this investigation. According to the theory, a partner’s positive emotions may act as a relational resource, fostering emotional connection and promoting resilience against stress.

“I am fascinated by Barbara Fredrickson’s Positivity Resonance Theory, which explains the dynamics—and the importance!—of shared positive emotions during social interactions. For anyone who is interested, her book Love 2.0 is excellent,” said study author Tomiko Yoneda, an assistant professor at the University of California, Davis, and head of the Healthspan Lab.

The researchers pooled data from three independent studies involving 321 older adult couples from Canada and Germany. Participants completed daily assessments over a week, including multiple saliva samples to measure cortisol and electronic surveys to report emotional experiences. Couples were mostly long-term partners, with relationships averaging 44 years. They were recruited under strict eligibility criteria to ensure both physical and cognitive health. Participants rated their momentary emotions—such as happiness, relaxation, or anger—on a scale, providing a snapshot of their emotional states throughout the day.

“I was particularly impressed by the participants’ adherence,” Yoneda said. “They completed short surveys on tablets and measured their own cortisol via saliva samples 5–7 times per day for 7 consecutive days. Despite the substantial burden, adherence was incredibly high, at 91–98% across the three sub-samples.”

The study captured how participants’ own emotional experiences influenced their cortisol levels and examined whether these associations extended to their partners. Cortisol levels typically follow a diurnal rhythm, peaking shortly after waking and gradually declining throughout the day. The researchers also measured total daily cortisol secretion, known as the area under the curve, to provide a comprehensive picture of participants’ stress physiology. Participants’ relationship satisfaction was also assessed to explore how relationship quality influenced the emotional-cortisol dynamics.

The results revealed that positive emotions experienced by one partner were linked to lower cortisol levels in the other partner, both moment-to-moment and throughout the day. “Our findings showed that when your partner is happy, it’s linked to you having lower levels of cortisol throughout the day,” Yoneda told PsyPost. “Importantly, this effect goes beyond the influence of your own happiness on your cortisol.”

Interestingly, while participants’ own negative emotions were associated with higher cortisol levels, their partner’s negative emotions showed no consistent effect on cortisol. This suggests that the influence of emotions within couples may be more pronounced for positive states, potentially due to their role in fostering connection and mutual support.

“We didn’t find any links between a person’s cortisol levels and their partner’s negative emotions, suggesting that older adults may shield or protect their partner from sharing, physiologically, in negative emotions,” Yoneda explained. “This aligns with research showing that older adults tend to focus on emotionally meaningful goals and regulate emotions more effectively, fostering more positive relationships in late life.”

Another key finding was the amplifying effect of age and relationship satisfaction. The association between a partner’s positive emotions and reduced cortisol was more pronounced in older participants and in those who expressed greater relationship satisfaction. This underscores the importance of emotional and relational contexts in shaping physiological responses, particularly during older adulthood when stress regulation becomes more challenging.

The study highlights the interconnectedness of emotional and physiological processes within intimate relationships but acknowledges some limitations. Most participants were healthy, long-term couples in heterosexual relationships, which may not represent the broader population of older adults. This homogeneity limits the generalizability of the findings to more diverse groups, including those in non-traditional or less satisfying relationships.

Additionally, the observational nature of the study means causality cannot be determined. The researchers cannot definitively say whether a partner’s positive emotions reduce cortisol or if lower cortisol levels contribute to more positive emotions in their partner.

Future studies could explore these dynamics in more diverse samples, including younger couples, same-sex relationships, or individuals with health challenges. Researchers might also examine how specific behaviors, such as physical affection or shared activities, mediate the connection between emotions and stress. Understanding these mechanisms could help develop interventions that harness the emotional benefits of relationships to promote health and resilience as we age.

“I am interested in investigating how psychological and physiological processes are intertwined in relationship partners to identify ways in which personality factors and emotions can act as a social resource that may subsequently lead to optimal aging and development,” Yoneda said.

“This research would not have been possible without my incredible team of co-authors!” she added.

The study, “‘What’s yours is mine’: Partners’ everyday emotional experiences and cortisol in older adult couples,” was authored by Tomiko Yoneda, Theresa Pauly, Nilam Ram, Karolina Kolodziejczak-Krupp, Maureen C. Ashe, Kenneth Madden, Johanna Drewelies, Denis Gerstorf, and Christiane A. Hoppmann.