I found it while reading this HBR piece: "Practical Tips for Overcoming Resistance."
From the book:
The results of a recent study of 3,682 couples [...] found that women who give up and give in during arguments with their husbands are four times more likely to die prematurely than women who argue productively. The women who held it in also had a higher risk of depression and irritable bowel syndrome. The study's authors conclude that healthy arguments are good for your health and longevity.