A study of 1,981 middle-aged heterosexual couples revealed that people who had happy spouses were notably more likely to report better health over time.

"This finding significantly broadens assumptions about the relationship between happiness and health, suggesting a unique social link," said the study's principal investigator Professor William Chopik, who teaches psychology at Michigan State University. "Simply having a happy partner may enhance health as much as striving to be happy oneself."

Building on the previous findings that happy people are generally healthy, Chopik wanted to zero in on the effects that interpersonal relationships have on health. He sees at least three reasons why a happy partner might make you healthier (even if you are not happy yourself): happy partners can provide more support, they might get the unhappy people involved in healthy activities like sleeping and eating well, as well as exercising. And lastly, it's just easier to deal with happy people.

"Simply knowing that one's partner is satisfied with his or her individual circumstances may temper a person's need to seek self-destructive outlets, such as drinking or drugs, and may more generally offer contentment in ways that afford health benefits down the road," said Chopik.

The study's six-year survey involved couples from 50 to 94, with 84% of the participants being white, 8% African-American and 6% Hispanic. There were no differences shown between husbands and wives. 

The authors themselves caution that more research needs to be done. In particular, the paper warns that "causality cannot be definitively discerned with these data" and hopes that future studies will also look at different groups of people, not just the mainly older white married couples. The researchers also propose that new studies on the subject could benefit from using data that is gathered in a more objective way than being self-reported. 

You can find the study here, in the journal of the American Psychological Association.