The biggest lesson from the world’s longest scientific study of happiness

If you could design a life full of happiness, what ingredients would you choose? Many people would fill it with lots of money, long vacations, a successful career, and a lifestyle of status, leisure and ease.

But that leaves out the most important engine of happiness, the world’s longest scientific study on the subject has found.

Most people aren’t aware of this true ingredient because our culture sells us messages that aren’t true, like “buy this thing and you’ll be happier,” says Dr. Robert Waldinger, a clinical professor of psychiatry at Harvard Medical School in Boston.

He’s the director of the Harvard Study of Adult Development, which began in 1938 with 724 participants and set out to discover what makes people thrive.

Eighty-five years later, the study includes three generations and more than 1,300 descendants of the original participants. People have been followed from their teen years to old age, with researchers gathering everything from their exercise and drinking habits, to marital satisfaction and biggest worries.

Researchers regularly collect their health records for markers of physical and mental well-being, and meet them face-to-face to observe their behavior and living conditions.

Participants rate their lives by answering questionnaires that ask whether they’re happy, if their life is meaningful and if they have a reason to get up in the morning. They undergo brain scans, blood tests and checks of stress hormones.

What did the healthiest and happiest participants have in common? The answers are distilled in Waldinger’s new book, “The Good Life: Lessons from the World’s Longest Scientific Study of Happiness.”

One factor stood out above everything else: Good relationships.

So if you were to make one decision to best ensure your own health and happiness, it should be to cultivate warm relationships, Waldinger and his co-author write.

“We think it’s because relationships help us manage stress,” Waldinger tells TODAY.com.

“Following thousands of lives over decades, we see that every life has difficulties. So the question is not: Do you have challenges? The question is: How can you meet those challenges? Do you have the resources that you need to meet those challenges? We say that one of the strongest resources to meet challenges is having good relationships.”

Here are the key messages from the book:

It’s not necessarily about being married or living with someone, since people can be lonely in a marriage and thrive by living alone. But it’s important to have friends and loved ones you can talk with and rely on.

“Really, what you need is somebody in your life who you can call on. In fact, we asked our study participants: Who could you call in the middle of the night if you were sick or scared? Some of our folks could list several people, and some of our folks couldn’t list anyone — not a soul in the world,” Waldinger says.

“We think that everybody needs at least one person in their life who they feel is a safety net for them, who would have their back if they were really in trouble.”

People who don’t have that support can end up chronically stressed, which can make their health suffer.

Don’t underestimate the power of casual connections — like talking with a stranger on a plane or exchanging little pleasantries with the barista who makes your coffee. These interactions give us little hits of well-being, research has found.

“There’s something about a positive response from someone else that makes us feel good,” Waldinger says. “(But) we often think those don’t really matter and we ignore that little bit of well-being we get.”

It's not about 100% leisure and relaxation. The people who are the happiest and have the greatest sense of well-being are those who find life brings challenges they can meet, the study researchers found. The biggest satisfaction often comes from doing hard things like raising children or starting a business.

“If life brings challenges that are interesting, that allow us to feel like we’ve accomplished something, that’s very satisfying,” Waldinger says. “Wealth and privilege don’t buy you happiness.”

One is all about being happy right now, as in: Am I enjoying myself right this minute? That’s called hedonic well-being — related to hedonism.

The other bucket refers to deep well-being where a person feels their life is satisfying and meaningful regardless of what else is going on outside of the current moment, Waldinger and his co-author write. This is called eudemonic well-being.

Here’s an example of the difference: Let’s say you’re reading to your child to get her to go to sleep. You’ve read the book seven times, but she begs you to read it for the eighth time.

“You’re exhausted, you’ve had a long day and you’re falling asleep. Are you having fun doing this for the eighth time? No, so it’s not hedonic well-being. But is this the most meaningful thing you could imagine doing at that moment? Yes,” Waldinger says.

“If you’re not happy all the time, that doesn’t mean you’re doing something wrong… that’s just the truth of being alive,” Waldinger says.

“We can improve our lives and we can improve our happiness for sure. But we don’t have to expect ourselves to always be happy.”

Also remember that everyone faces stress and challenges, so even though it seems like other people have it all figured out and are happy all the time, that’s just not true, he adds.

For many people, work occupies more of their waking hours than anything else, so work relationships are important, the Harvard study found.

“This is backed by really good research that shows that having a personal friend at work makes a huge difference in our well-being,” Waldinger says.

As the study has followed people for 85 years, researchers have watched thousands of lives unfold from adolescence to old age.

“What we’ve seen is that it is never too late. There are people who thought they were no good at relationships, who always felt like they were alone,” Waldinger says.

“Then when they least expected it, they would find a new group of friends that they never had before, or they would find love. Sometimes people for the first time in their 60s, 70s, 80s would find these things… so the message that comes from our research is: If you think it’s too late for you to have better relationships, think again.”