Finding the secrets to a happy life can literally take a lifetime. After 88 years, the world's longest study on happiness is still going strong.
In 1938, scientists at Harvard University put together a study to compare the lives of two groups of young White men: one, a privileged cohort of Harvard students (including John F. Kennedy, before he was president), and the other, an underprivileged cohort of teenagers from one of Boston's poorest neighborhoods during the Great Depression.
Over the decades, the Harvard Study of Adult Development has added hundreds more participants to its roster, including women and children, and the research is still ongoing.
It is now arguably the longest study of adult life that's ever been conducted. It's taken several generations of scientists and four directors to keep the research going, and it has an extremely low dropout rate that is almost unheard of for a study this long.
After eight decades, hundreds of peer-reviewed papers, and countless questionnaires, medical check-ups, and in-person interviews with participants, the team has accumulated important clues about what best predicts health and well-being in late life.
Across the board, the best predictors of a happy and meaningful life were not wealth, fame, hard work, intelligence, or even 'good' genes.
Instead, about 30 years ago, the research team began to find a surprising connection between close relationships and how good our lives feel to us.
The research can't prove that relationships cause happiness or good health, but the patterns are certainly suggestive.
When the researchers gathered all the data they had on their participants at age 50, they found it wasn't physical health, such as cholesterol levels, that best predicted how long someone would live; it was how satisfied they were in their relationships.
Those people most satisfied with their community of friends and family in middle age were the healthiest at age 80, less likely to have diseases, and more likely to recover from illnesses.
"We didn't believe the data at first," recalled psychiatrist Robert Waldinger, the current director of the study, in a TED Talks video from 2023, which has accrued over 1 million views.
"How could this be that relationships actually get into our bodies and shape our health?"
Over and over again, however, it was clear that connection to family, friends, and community tended to lead to longer, happier, and physically healthier lives. Evidence from other studies also began to roll in, suggesting that relationships can keep people physically stronger and their brains sharper as they age.
The experience of loneliness, by contrast, has emerged as a significant risk factor for poor well-being. Some studies now estimate that loneliness and social isolation can increase the risk of premature death by more than 25 percent. Other studies suggest isolation can change the very function and structure of our brains.
Still, surrounding yourself with a huge number of people so that you are never alone isn't the answer, either. It's all about the quality of relationships you foster, Waldinger explains.
In a 2010 peer-reviewed study, Waldinger and clinical psychologist Marc Schulz, associate director of the Harvard Study of Adult Development, explored what their team had found among 47 married couples in their 80s.
Those individuals who were more satisfied in their marriages showed a stronger ability to withstand the negative effects of poor health on their happiness. Conversely, those who were dissatisfied in their marriages were more likely to experience unhappiness due to poor health.
In other words, satisfying relationships may act like protective buffers against the stresses and anxieties of life.
Critics, however, argue that the results of the Harvard Study of Adult Development are oversimplified and apply mainly to a small cohort of mostly White people in the United States during a very specific time in history.
Measuring what makes a 'good' or 'satisfying' relationship is tricky work, and it will be even more challenging to directly tie those feelings and emotions to health outcomes.
In all likelihood, there's no universal secret to health or happiness, but a decades-long study that follows hundreds of people can still provide us with real wisdom.
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"The original founders of this study would never have believed that I'd be sitting here today telling you that our scientific work is still going on with these same families," Waldinger said in a 2024 interview.
For its ninth decade of life, the Harvard Study of Adult Development plans to continue "its voyage of discovery," adding new data to its "treasure trove" and enabling "people to live healthier lives filled with meaning, connection, and purpose."
That's something to smile about.