The study began in 1938 and continues to follow participants and their descendants
Since 1938, Harvard scientists have been observing the lives of hundreds of people and their descendants — and this is the longest study of happiness in history. Over 88 years, thousands of questionnaires, medical records, and interviews have been accumulated. The main conclusion surprised even the researchers themselves: neither wealth, nor fame, nor intelligence turned out to be the best predictors of a happy life.
The Longest Study of Happiness
In 1938, at the height of the Great Depression, scientists at Harvard University launched a large-scale project. They recruited two groups of young white men: 268 Harvard students (the privileged elite) and 456 teenagers from the poorest neighborhoods of Boston. Among the participants of the first group, incidentally, was future U.S. President John F. Kennedy.
The study is called the Harvard Study of Adult Development. Over 88 years, it has been led by four directors, and the participant pool has grown from hundreds to thousands: wives were added, and then the children of the original participants — more than 1,300 second-generation individuals. The project is currently directed by psychiatrist Robert Waldinger.
Such longevity is almost unprecedented. Most long-term studies wind down within ten years because participants stop showing up. The Harvard study, however, maintains an extremely low dropout rate, which makes its data especially valuable.
What People Need to Be Happy
When the project first began, scientists were convinced that health and success in life were determined by physical condition, intellect, and heredity. The first researchers measured skulls, analyzed handwriting, and recorded the functioning of internal organs.
But decades of observation revealed a completely different picture. When the team gathered all the data on participants at age 50, it turned out that the best predictor of a long life was not cholesterol levels or genetics, but how satisfied the person was with their relationships: with a partner, friends, and family.
Those who were satisfied with their circle of close people in middle age turned out to be healthier by age 80, got sick less often, and recovered from illnesses faster. In Waldinger’s words, “we didn’t believe the data ourselves at first.”
Relationship quality turned out to be a stronger predictor of health than physical indicators. Image source: ig-store.ru
How Relationship Quality Affects Health and Longevity
One of the most specific results of the study is related to marriage. In 2010, Waldinger and clinical psychologist Marc Schulz studied 47 married couples whose participants were in their 80s. It turned out that those who were satisfied with their marriage coped better with physical pain: even on days when the pain was severe, their mood remained stable. But for those who were unhappy in their marriages, physical pain intensified emotional suffering.
In other words, satisfying relationships function as a kind of buffer — a protective mechanism against stress, anxiety, and the physical difficulties of aging. This is confirmed not only by the Harvard data: other studies show that social connections help maintain mental sharpness with age and slow cognitive aging.
What matters is not the number of contacts, but their quality. As Waldinger explains, surrounding yourself with many people is not a cure for loneliness. What’s important is having people you can count on, and relationships that bring warmth and support.
IMPORTANT TO NOTE: the study does not prove that relationships directly cause happiness or good health. It's about correlation — a consistent association that appears in the data again and again. But the pattern is so pronounced that it's hard to ignore.
How Loneliness Is Dangerous for Health
The flip side of this discovery is no less striking. Loneliness and social isolation are a serious risk factor not only for mental health but also for physical health. According to a large meta-analysis combining results from numerous studies involving more than 3.4 million people, social isolation and loneliness increase the risk of premature death by approximately 26–32%.
Some studies show that isolation can literally change the structure and function of the brain. And the World Health Organization in 2025 released a special report calling loneliness “a defining challenge of our time”: according to WHO estimates, one in six people on the planet suffers from it.
Waldinger puts it simply:
Loneliness kills. Its impact is comparable to smoking or alcoholism.
This is not a metaphor, but a reflection of statistical data showing that chronically lonely people objectively live shorter lives.
What Critics Say About This Happiness Study
For all its scale, the Harvard study is not perfect. Critics rightly point to several limitations.
- The original sample consisted exclusively of white men from one city and one country in a specific historical period. How universal these conclusions are remains an open question.
- The concepts of “good relationships” and “satisfaction” are difficult to measure objectively. These are subjective assessments that can change over time.
- Directly linking emotional states to specific diseases is a methodologically challenging task, and correlation does not equal causation.
In recent years, the participant composition has become more diverse — it now includes women, children of participants, and more than 1,700 people from various social and ethnic groups. But the conclusions based on the first decades still rely on a limited group.
Nevertheless, it is precisely the duration and depth of observations that make this study a unique resource. Following the same people throughout their entire lives, from youth to old age, has never been achieved by anyone else.
How to Become a Happy Person
The book by Waldinger and Schulz, “The Good Life,” based on the study’s results, became a New York Times bestseller. Waldinger’s TED talk has garnered more than 42 million views and is among the ten most popular TED talks in history. This indicates that the topic strikes a nerve — people want to understand how to live a good life.
The practical takeaways from 88 years of observation seem deceptively simple:
- Invest time and attention in relationships — with family, friends, colleagues, neighbors. Even shallow but warm everyday interactions matter.
- Quality over quantity: a few truly close people are worth more than a hundred superficial acquaintances.
- It’s never too late to start: among the study participants were people who found close friends and love in their 70s and 80s.
- Introverts need relationships too — just fewer of them. Loneliness and introversion are different things.
Warm relationships with loved ones are one of the strongest predictors of a long and healthy life
The study continues into its ninth decade. Its authors are examining how childhood experiences affect health in adulthood, how parents’ marriages are reflected in their children’s relationships, and how new generations build their lives in the digital age.
