Have you ever wished you could fast-forward your life so you could see if the decisions you’re making will lead to satisfaction and health in the future? In the world of scientific research, the closest you can get to that is by looking at the Harvard Study of Adult Development — a study that has tracked the lives of 724 men for 78 years, and one of the longest studies of adult life ever done. Investigators surveyed the group every two years about their physical and mental health, their professional lives, their friendships, their marriages — and also subjected them to periodic in-person interviews, medical exams, blood tests and brain scans.

The big takeaways from that talk: Good relationships keep us happier and healthier, and loneliness kills. But there were, of course, many more lessons to be learned — the study has yielded more than 100 published papers so far, with enough data for “scores more” — and Waldinger shares four of them here. 

1. A happy childhood has very, very long-lasting effects.

Having warm relationships with parents in childhood was a good predictor you’ll have warmer and more secure relationships with those closest to you when you’re an adult. Happy childhoods had the power to extend across decades to predict more secure relationships that people had with their spouses in their 80s, as well as better physical health in adulthood all the way into old age. And it’s not just parental bonds that matter: Having a close relationship with at least one sibling in childhood predicted which people were less likely to become depressed by age 50.

2. But … people with difficult childhoods can make up for them in midlife.

People who grow up in challenging environments — with chaotic families or economic uncertainty, for instance — grew old less happily than those who had more fortunate childhoods. But by the time people reached middle age (defined as ages 50–65), those who engaged in what psychologists call “generativity,” or an interest in establishing and guiding the next generation, were happier and better adjusted than those who didn’t. And generativity is not dependent on being a parent — while people can develop it by raising children, they can also exhibit it at work or other situations where they mentor younger adults.

– Daryl Chen

Read More: 4 lessons from the longest-running study on happiness

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