The Harvard Study That Should Change How You Think About Success

Harvard Study Findings

The Harvard Study of Adult Development, now in its 87th year, is the longest-running study of adult life ever conducted. Its central finding is that the quality of close relationships is the single strongest predictor of someone’s health, happiness, and longevity. These results have been well replicated and have been controlled for wealth, IQ, class, and professional achievement.

• Warm relationships in midlife predicted better physical and mental health at 80,
• Relationship satisfaction at 50 was a better predictor of health at 80 than cholesterol levels,
• Lonely people’s brains declined earlier,
• Those with closer relationships maintained sharper cognitive function for longer.

The quality of connection matters far more than quantity. The implications for how we define success — individually and societally are huge. And, to be honest, we’re not really acting on this knowledge, though many of us kind of intrinsically know it to be true.

The Study Itself

In 1938, a group of researchers at Harvard began tracking the lives of 268 sophomore students. They wanted to understand what factors predicted a good adult life. The study has continued ever since. It’s spanned the Depression, the Second World War, the post-war boom, the social revolutions of the 1960s and 1970s and the digital age. It’s followed not just the original cohort but their children and grandchildren, expanding eventually to include over 1,300 people. It is the longest-running study of adult development ever conducted, and after more than eight decades of data, its principal conclusion is striking in its simplicity: the quality of our close relationships is the single most powerful determinant of whether we live healthy, happy, long lives.

Robert Waldinger and Marc Schulz, who now lead the study, published their account of its findings in 2023 in a book called The Good Life. What they describe is not merely an academic conclusion. It is a direct challenge to the way that most individuals, and most organisations, define and pursue success.

What 85 Years of Data Tells Us

The Harvard Study began with two cohorts that could hardly have been more different.

• The first was the group of Harvard sophomores, predominantly white, male, and from relatively privileged backgrounds (I think a young JFK was in this cohort).
• The second, added later, was a group of boys from some of Boston’s most deprived inner-city neighbourhoods.

By following people with such different starting points across the same long arc of life, the researchers were able to distinguish between factors that appeared to matter and factors that actually mattered when everything else was held constant.

The findings on relationships emerged not from a single dramatic discovery but from the steady accumulation of evidence over decades. Participants who reported warmer, more satisfying relationships in their 40s and 50s were consistently healthier and happier in their 70s and 80s. Those who described their marriages and friendships as cold, conflictual, or distant were more likely to experience chronic illness, cognitive decline, and premature death. The relationship between social connection and health outcomes proved to be more robust and more consistent than the relationship between health outcomes and almost any other variable the study tracked — including wealth, educational attainment, IQ, and professional success.

One finding in particular has stayed with researchers and readers of the study alike. Relationship satisfaction at age 50 turned out to be a better predictor of physical health at age 80 than cholesterol levels at 50. Bonkers. The quality of a person’s closest relationships in midlife predicted their physical health in old age more accurately than a standard medical biomarker. This is one of the most concrete illustrations of the mind-body connection in the empirical literature (Darned Descartes).

The Relationship-Health Mechanism

How does relationship quality translate into physical health outcomes? The Harvard Study does not by itself establish mechanism. But a large body of complementary research sheds some light on how social connection affects physiology.

Close relationships serve as a buffer against stress. When people face difficulty — financial pressure, health scares, professional setbacks, bereavement — the availability of warm, supportive relationships moderates the physiological stress response. Cortisol levels are lower. Inflammatory markers are reduced. The cardiovascular system recovers more quickly from acute stress. The presence of trusted others quite literally changes the chemistry of the body’s response to threat.

Relationships also influence behaviour in ways that compound over time. People with close, supportive relationships are more likely to eat well, exercise, attend medical appointments, take prescribed medication, and avoid harmful coping behaviours. They are less likely to smoke heavily, drink excessively, or make persistently poor health decisions in isolation. The warm relationship is not just emotionally sustaining; it is a practical accountability structure that nudges people towards better health choices over decades.

The cognitive findings from the Harvard Study are equally significant. Participants who reported more satisfying relationships in their 60s maintained sharper memories and clearer cognitive function in their 80s. Lonely people’s brains declined earlier and more steeply. The research aligns with broader evidence on social engagement and cognitive health: the social brain is an active brain, and isolation, over time, accelerates the neurological deterioration that leads to dementia and cognitive decline. Social connection is not merely pleasant. It appears to be neurologically protective.

Quality Not Quantity

One of the most practically useful findings from the Harvard Study is the primacy of quality over quantity in social relationships. The healthiest and happiest participants were not those with the most friends, the busiest social calendars, or the most extensive professional networks. They were those who had a small number of relationships characterised by genuine warmth, trust, and reciprocity.

This distinction matters enormously in an age of quantified social life. LinkedIn connections, follower counts, the size of one’s professional network: these are the metrics through which many people now assess their social standing. But my god they are sh*t. I feel it and I’m sure you do too – many of them are just the chaff of life, or worse than, time consuming chaff. By the Harvard Study’s evidence, they largely irrelevant to the outcomes that actually matter. A person with five hundred professional acquaintances and no one they could call in a genuine crisis is, by the study’s measures, socially impoverished. A person with three deep, warm friendships is not.

Waldinger and Schulz are careful to note that the study does not prescribe a particular kind of relationship. What mattered was not marriage per se, or friendship of a specific type, but the experience of being known and valued by someone, of having relationships in which you could be honest and vulnerable, in which conflict could be navigated without the relationship being destroyed, and in which mutual care was genuine rather than performed. These qualities can be found in long marriages, close friendships, and strong family bonds, and they can be absent from all of them. The form of the relationship matters less than its quality.

What This Means for How We Define Success

The typical markers of a successful life: wealth, status, professional achievement, career advancement are actually pretty poor predictors of the outcomes the study measured. Participants who pursued status and wealth at the expense of relationships were not, in later life, happy or healthy. Participants who prioritised relationships, who made time for the people they cared about, who invested in maintaining connections, who were willing to sacrifice professional advancement for relational richness, did better on almost every measure. Again, this isn’t new knowledge.

Waldinger has noted in interviews that many participants in the study, when asked in their 70s and 80s what they would change about their lives said they wished they had worked less and had spent more time with the people they loved. They wished they had invested in relationships with the same seriousness that they had invested in their careers.

The People Shift View

What does the Harvard Study mean for organisations? I’m not so sure really.

I think we’re all responsible for our own relationships and those of our friends. I also think that as society we have a responsibility to create space and opportunity for these relationships. As society we should work to create cultures that foster these relationships and to regulate factors that are detrimental to them (as we are with social media). It’s clearly the case that the lack of strong relationships damages health and, in turn, create a financial burden. So it’s not just in the moral interest of societies to support relationships, it’s also in their financial interest.

But should orgs have a role in this? I don’t really know that they should feel obliged to do so. I suspect that doing so would lead to greater attraction and retention of talent, and improved engagement and organisational resilience. But that doesn’t mean it’s necessarily right for orgs to try and foster such connections. Some leaders will want to create spaces that do so, some won’t, and that is fine. If orgs damage their people, then the cost will fall on society. If orgs create great places with strong connections, those benefits accrue to society.

Regardless of what we feel it is right for orgs to do, it feels like all of us should act a bit more on this information as individuals and focus on our own relationships, while helping others do so too.

Learning More

To go deeper, explore these resources on people-shift.com:

• Wellbeing
• Subjective Wellbeing
• Employee Engagement
• Bowling Alone
• Dunbar’s Number