In today’s video, I’m going to talk about the #1 key to long-term health and happiness, according to the world’s longest research study on human flourishing.

Read or watch below to learn about the key to long-term happiness.

Zachary Stockill: Scientists and researchers have recently discovered the number one key to human health and long-term happiness.

In today’s video, that’s exactly what I’m going to talk about.

Harvard’s Study of Adult Development is the longest-running research study on human beings.

It was started back in the 1940s, a very long time ago, at Harvard University. A group of Harvard researchers and psychologists started doing a yearly or bi-yearly survey of the graduating class.

They started surveying these men every single year about their lives, asking them very intimate questions about what they spend their time doing, who they’re spending their time with, what they do for work, their income levels, all these things.

They really go into great detail in terms of what makes these people tick over decades and decades and decades. And even though it started in the 1940s, this study is still ongoing today because some of these men are still alive.

And what’s more, many of the participants’ children, and even their grandchildren have started participating in this unique and groundbreaking study on what makes a good life. This is the longest-running study on the key to long-term happiness, by a mile.

The major discovery of the Harvard Study on Adult Development is quite simple. There is a number one key to a great life. There is one factor above all others.

It is the greatest predictor of human health, happiness, and flourishing.

And that is: the quality of one’s relationships.

We’re not just talking about your intimate relationship in terms of your partner, your spouse, your boyfriend, girlfriend, husband, wife, or anything like that…

The quality of all of the close relationships in your life. So not only your intimate partner but also your friends and your family.

The more people report satisfaction in their relationships, the more people report having relationships in the first place, and the more people report having invested time and effort into maintaining those relationships, the healthier those people were, and the happier there were.

We are a social species to the core. We are among the most social species on the planet.

But even the most introverted among us not only want close relationships, close friendships, and intimate partners, this kind of thing… We actually need them for our own human flourishing at a deep level.

The better our intimate relationships are, the better our life is, and the happier and the healthier we’re more likely to be.

So what does this mean for all of us?

What I’m taking away from this study, and what everyone watching this video could potentially take away from this study, is we should spend more of our lives investing in our close relationships. Not just our intimate partner, but our friends or family members. Because, over time, this will pay enormous dividends in terms of our overall sense of mental and physical health, happiness, and well-being.

Think of the three closest relationships in your life. Now, one of these can be your intimate partner, if you have an intimate partner. But also think about, for example, close friendships. These can be friends that you feel particularly close to. Maybe you see them every week, or maybe it’s been a long time since the last time you connected with them.

Do a little Google search on the average life expectancy for your gender in your country…

So I’m Canadian. The average life expectancy for Canadians is around 78 for Canadian men, the last time I checked. So if I do a little arithmetic, and about the average life expectancy of my friend…

If you do a little bit of simple maths, you might realize that you might not be able to spend that much time with this person over the coming years.

…Unless you prioritize it.

Maybe you fell into a pattern where you kind of let those friendships slip away, or you’re not investing the time in your intimate relationships that maybe you should be.

So personally, I’m taking my list of three people, and I’m taking active steps to make that more of a priority. So for me, that might mean buying an extra plane ticket or two every year. It may mean scheduling another week off when maybe, in the past, I would have avoided taking another week off…

I started a monthly Zoom call with about three or four of my closest friends. So I have a one-hour Zoom call, approximately, with three or four of my closest friends every month, like clockwork. And I want to emphasize I’m an introvert. I’m very happy to spend a week totally by myself, writing and reading, and cooking for myself. Just kind of stay in my little hole. I’m quite happy doing that.

But I know that I feel more energized, and I feel more connected to my community, when I’m taking active steps to invest in my intimate relationships, in my friendships, and of course, in my romantic relationship as well.

So try the same for yourself.

Key to long-term happiness

Think about three relationships that you want to invest more in, in the years to come.

And then, crucially, make it a priority.

Write down in detail exactly how and why you’re going to prioritize these relationships over the coming years. And the exact steps you’re going to take to make them more of a priority.

It’s fair to assume that your long-term happiness, and maybe even your health will benefit as a result.

If you need more help to get clarity and insight, consider applying for one-on-one coaching with me.

Zachary Stockill
Zachary Stockill

Hi! I'm a Canadian author and educator whose work has been featured in BBC News, BBC Radio 4, The Huffington Post, and many other publications. I'm the founder of, the author of Overcoming Retroactive Jealousy and The Overcoming Jealousy Workbook, and the host of Humans in Love podcast.