What's a better predictor of health? Friendship or cholesterol levels? "This shared global moment has illuminated how significant friends are to day-to-day happiness. Science has been accumulating evidence that friendship isn’t just critical for our happiness but our health and longevity. Its presence or absence matters at every point in life, but the cumulative effects of either show up most starkly in the later stages of life." Author Lydia Denworth reflects.