Notably, in the second study (which focused on older adults, specifically), it was found that when friends were the source of tension or stress, people reported more chronic illnesses, while when someone felt supported by their friendship, they reported fewer health issues and increased happiness. (Like when they help you get through a tough workout. Yep, exercising with a buddy can increase your pain tolerance.) It's important to note, however, that the researchers did not draw a clear line between one causing the other—a.k.a. a falling out with your friend won't necessarily make you sick.
