In 2017, the American Heart Association ran a study tracking the progression of heart disease amongst married and unmarried individuals. The study found that single, unmarried individuals were significantly more likely to suffer heart attacks or death from cardiovascular illnesses. A purported theory for this phenomenon lies in the connection between heart disease and stress. Heart diseases are exacerbated by stress, and individuals in happy, healthy relationships are often less stressed than their single counterparts. This is because having a reliable, understanding, and trustworthy confidante can work wonders at reducing and mitigating stress or stress-related symptoms.
Physical intimacy has also been found to aid in heart health. As Penn Medicine reported, acts of physical intimacy such as hand-holding, kissing, and sex can trigger the release of various endorphins in the body, which can ultimately help counter heart disease and even depression. Similarly, a 2010 study conducted by PLOS Medicine found that individuals with stronger, closer social relationships, such as marriage and intimate relationships, typically live 50% longer than those with more sparse social relationships.