You know the saying “What’s yours is mine”?

Well, it seems like that might be true for more than just your husband’s socks.

A recent study published in the journal Psychoneuroendocrinology found that your partner’s good mood can make you feel happier as well.

Researchers analyzed the data of 321 couples from Germany and Canada and discovered that when someone’s partner was feeling peppier than usual, it decreased their own levels of cortisol — the stress hormone — even if they weren’t feeling so great to begin with.

This effect was even more pronounced among older adults who reported higher levels of relationship satisfaction.

What’s interesting to note is that the inverse wasn’t necessarily true — meaning there was no observed association between someone’s bad mood and their partner’s cortisol levels.

The participants weren’t exactly spring chickens in the midst of their honeymoon period either — they were aged between 56 and 87, and the average length of the relationships was 43.97 years.

As such, lead author Tomiko Yonedaan assistant professor of psychology at the University of California in Davis, believes the findings suggest that older couples in long-term, committed relationships find ways to protect one another from the impact of negative emotions.

This is significant, as adults can often find it harder to regulate their moods as they age. Cortisol tends to stay elevated for longer periods in older adults after a stressful event, and an aging brain may struggle to adapt to stressors over time.

When you add the effects of chronic physical pain, reduced mobility and social isolation — it can be a pretty miserable experience.

These results highlight the importance of trying to maintain a good mood around your spouse — as it can act as a psychological buffer to age- stress.

“Having positive emotions with your relationship partner can act as a social resource,” Yoneda said.

This isn’t the first time science has emphasized the health benefits of a joyful partner.

A 2016 study found that people with happy spouses were more likely to report better health over time, regardless of their own happiness levels.

Similarly, an 85-year-long Harvard research project concluded that happy marriages are the key to long, healthy lives.