George Vaillant conducted one of the longest-duration longitudinal studies in history. Over 75 years he has studied a group of almost 300 Harvard grads to identify what contributes to health and happiness. A parallel study of almost 500 disadvantaged youth in inner city Boston confirmed that the conclusions were class-independent. What he discovered was that warmth of relationships throughout life have the greatest positive impact on ‘life satisfaction’. He summarized it: “Happiness is love.”