White, heterosexual men have the fewest friends of anyone in America. This “friendship crisis” matters: Loneliness and social isolation can kill. Friendships ― especially those initiated during childhood ― coincide with better adult health. As people age, their social networks begin to thin out, and if you had few friends to begin with, you may become socially isolated, which is associated with a higher risk of ailments such as heart disease, stroke and cancer.