The Harvard Study of Adult Development is a very long study of people's lives. It began in 1938 with 724 participants. Of these, 268 were sophomores (second-year students) at Harvard College, and 456 were young adults from Boston. Today the study also includes 1,300 descendants of the original participants, so the researchers can learn from more than one generation.

The researchers followed the participants for many years and studied what made their lives happy and healthy. The main result is simple. Close relationships, more than money or fame, keep people happy throughout their lives. This means that people need good relationships more than a big bank account.

The researchers also found a link between relationships and health. The people who were the most satisfied in their relationships at age 50 were the healthiest at age 80. Robert Waldinger, a director of the study, said that satisfaction in relationships was the best predictor of a happy and healthy life. In other words, how happy people are with their relationships at age 50 can tell us a lot about their later life.

Waldinger says that everybody needs at least one solid relationship, with someone they can count on in times of need. He and his colleagues think that loneliness may be as dangerous to health as smoking half a pack of cigarettes a day. Harvard Health suggests volunteering for a favourite cause as a way to broaden your social life.