This is a story about the study of happiness, the key thing that stops most of us from getting more of it, and the most recent science that suggests the one simple habit we should all adopt.

Unfortunately, a vast majority of Americans never even try it. (Although, maybe that's good news: room for growth!)

Starting in the late 1930s, a team of researchers has been tracking a total of 268 Harvard graduates from the classes of 1939 to 1944, along with 456 young men who happened to have been growing up in inner city Boston around the same time.

Over time, it's turned into one of the most extensive longitudinal studies ever, and has revealed a trove of insights. Perhaps the most famous and useful insight is this oft-repeated quote by Robert J. Waldinger, who is the current head of the study:

"The clearest message that we get from this 75-year study is this: Good relationships keep us happier and healthier. Period."

That's wonderful, right? But how do you fix your life if you don't happen to have good relationships?

An 'epidemic of loneliness'

To be honest, this is what's bugged me about this study for a long time: the clarity of the answer with no real guidance on how to get there.

Because it's one thing to say if you want to be happy, nurture good relationships. 

And it's another to suggest that with a straight face in the context of the "epidemic of loneliness" that Americans largely feel today, in the words of more than one writer.

A few alarming statistics from the federal Health Resources and Services Administration, just to back this up:

  • 40 percent of Americans say they "sometimes or always feel their social relationships are not meaningful."
  • 20 percent describe themselves as, "lonely or socially isolated."
  • 28 percent of older adults live alone.
  • From a pure physical health perspective, researchers say loneliness is as bad for you as smoking 15 cigarettes a day.

Oh, and here's another big one: According to a survey by Cigna last year, only about 50 percent of Americans have "meaningful in-person social interactions" on a daily basis -- and the numbers are worst for Generation Z.

I think a lot of us have had times in our life when we just felt alone. Sometimes it's through no fault of our own; sometimes it might be because we screwed up.

But so what? This isn't about assigning blame. It's about finding a way to help people improve their lives. 

How are you supposed to nurture good relationships if you find yourself in a rut where you don't have that many relationships to begin with?

Can I have a volunteer?

Finally, it seems that science has come up with an answer. The key way that people seem to be able to break the cycle of loneliness and begin to develop good relationships is to volunteer.

Yep, it's that simple. A recent study of 10,000 people in the United Kingdom reported that two-thirds said volunteering "helped them feel less isolated," according to Kasey Killam's recent survey in Scientific American

Separately, a U.S. study involving 6,000 widowed women found that those who started volunteering for just two hours or more per week found that "their average level of loneliness subsided to match that of married adults."

What's more, volunteering was especially helpful for older people, who are more likely to be lonely in the first place. And perhaps not surprisingly, it turns out volunteering is scalable: the more often you volunteer, the more relationships you're likely to develop.

Why it works

Most obviously, volunteering is simply an opportunity to meet other people, which is sort of a prerequisite to developing good relationships. 

You're also meeting people under altruistic circumstances, where by definition you're there for something other than your own benefit. 

Volunteering also combats the "loss of meaning" that often accompanies loneliness, as Killam summarizes. "By volunteering for social causes that are important to us, we can gain a sense of purpose, which in turn may shield us from negative health outcomes."

Finally, people who volunteer and thus combat loneliness and develop relationships are less likely to develop cognitive decline. Volunteering leads to increased engagement and stimulation, which in turn can help with relationships.

Like a lot of things in these prescriptive science-based studies, it's easier to talk about spending some time volunteering than it is to actually do it. 

But if you're not happy, and you find you don't have the good relationships that the Study of Adult Development suggests are most important, at least now you've got a roadmap.