Harvard followed 800 people over the course of multiple decades and found 6 things that make people live longer, happier lives

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• Harvard followed 800 people for their entire lives to see what actually makes people live happier, healthier, and longer.
• One of the three samples of people — 268 Harvard graduates born around 1920 — was the longest prospective study of physical and mental health in the world.
• A second sample was the longest prospective study of "blue collar" adult development in the world.
• The third sample was the longest prospective study of women's development in the world.
• The overall study found six key factors that impact happiness and longevity, including relationships, education, and generosity. 

There's a lot of good advice on how to be happier or more productive or how to have better relationships. But tips on how to improve your whole life  — something that will last decades and experience countless unpredictable changes — those should be regarded with extreme skepticism.

The only way to really get some good insights would be to follow a lot of people for their entire lives and see what actually works. Luckily, somebody did ...

The Study of Adult Development combined three massive longitudinal studies — research projects that followed people from youth until old age — to figure out what makes a good life.

From Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development:

The Study of Adult Development is a rarity in medicine, for quite deliberately it set out to study the lives of the well, not the sick. In so doing it has integrated three cohorts of elderly men and women — all of whom have been studied continuously for six to eight decades. First, there is a sample of 268 socially advantaged Harvard graduates born about 1920 — the longest prospective study of physical and mental health in the world. Second, there is a sample of 456 socially disadvantaged Inner City men born about 1930 — the longest prospective study of "blue collar" adult development in the world. Third, there is a sample of 90 middle-class, intellectually gifted women born about 1910 — the longest prospective study of women's development in the world ... Like the proverbial half loaf of bread, these studies are not perfect; but for the present they are, arguably, the best lifelong studies of adult development in the world.

George Vaillant is a professor at Harvard Medical School and led the study for over 30 years. His book is Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development.

With almost a century of data on nearly 1,000 people, there are plenty of insights. We'll cover 6 big ones that can get you on your path to awesomeness. (Remember: skimming my blog posts voids the warranty. If you don't read the whole thing and your life goes on to be awful, you will know why.)

Forgive me for starting with something obvious, but it had such an impact that it cannot be ignored.

1. Avoid smoking and alcohol

Hi, my name is Eric and it was never my intention to write after-school specials but here we go: Kids, smoking is bad.

It was the #1 predictive factor of health.

From Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development:

In both male cohorts not being a heavy smoker before the age of 50 was the most important single predictive factor of healthy physical aging. Among the College men heavy smoking (more than a pack a day for thirty years) was ten times more frequent among the Prematurely Dead than among the Happy-Well. Yet if a man had stopped smoking by about age 45, the effects of smoking (as much as one pack a day for twenty years) could at 70 or 80 no longer be discerned.

And drinking too much doesn't only hurt your health. Over the long haul it makes you less happy and screws up relationships.

Some people drink because they have problems. But the study showed alcohol is also an independent cause of problems, not merely a result.

From Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development:

... prospective study reveals that alcohol abuse is a cause rather than a result of increased life stress, of depression, and of downward social mobility ... Alcohol abuse — unrelated to unhappy childhood — consistently predicted unsuccessful aging, in part because alcoholism damaged future social supports.

Maintaining a healthy weight increased lifespan and regular exercise boosted both longevity and happiness. Plain and simple: those things you know you're supposed to do to stay healthy? Do them.

(To learn more about the science of a successful life, check out my bestselling book here.)

Okay, obligatory obvious stuff out of the way. You have to keep yourself healthy. But you also have to keep your brain healthy. And maybe not for the reasons you might guess.

2. Years of education = good

It's probably no surprise that, on average, the Harvard men were healthier at age 70 than the underprivileged men. But here's the twist...

If you compared only the guys from both groups who attended college, the difference vanished.

From Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development:

... the physical health of the 70-year old Inner City men was as poor as that of the Harvard men at 80. But remarkably, the health of the college-educated Inner City men at 70 was as good as that of the Harvard men at 70. This was in spite of the fact that their childhood social class, their tested IQ, their income, and the prestige of their colleges and jobs were markedly inferior to those of the Harvard men. Parity of education alone was enough to produce parity in physical health.

This wasn't due to family income and it wasn't due to IQ. Pursuing more education led to better habits and healthier lives.

From Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development:

The components of education that appeared to correlate with physical health in old age were self-care and perseverance — not IQ and parental income. The more education that the Inner City men obtained, the more likely they were to stop smoking, eat sensibly, and use alcohol in moderation.

(To learn the two-word morning ritual that will make you happy all day, click here.)

Okay, prepare yourself: the next one can be a little sad for some people because we can't change the past ... or can we?

3. A happy childhood

How much someone was loved as a child predicted their adult income better than knowing what social class they were brought up in.

From Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development:

... for both the Inner City men and the Harvard men the best predictor of a high income was not their parents' social class but whether their mother had made them feel loved.

Many say that you can find out what someone is really made out of by seeing how they handle a really stressful situation. The Study of Adult Development found that the people who aged the best had coped well with something so horrific you wouldn't wish it on your worst enemy:

Adolescence.

From Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development:

Again, as I have followed the lives of the Inner City men, one of the best indicators of successful aging was how well they had adapted in junior high school. Of the 150 Inner City men with the best scores for coping in junior high school, 56 were among the Happy-Well and only 13 were among the Sad-Sick. Of the 19 Inner City men with the lowest scores for adolescent adaptation, only a single man was among the Happy-Well, and 11 men, three-fifths, were among the Sad-Sick or Prematurely Dead. Successful adolescence predicted successful old age.

Yes, all this kinda sucks for some people. Amazon doesn't sell Time Machines and me saying, "Well, you should have picked your parents better" is far from helpful. So if your childhood was less than perfect and your adolescence felt like a bad reality show, does this mean you're doomed?

No. What went right in childhood was much more predictive than what went wrong.

From Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development:

A warm childhood, like a rich father, tended to inoculate the men against future pain, but a bleak childhood — such as with a poverty-stricken father — did not condemn either the Harvard or the Inner City men to misery ... Perhaps the best summary statement is, What goes right in childhood predicts the future far better than what goes wrong.

And there's even more reason for hope. Sometimes love and support come late — but that can be enough to heal old wounds.

When people found a loving spouse or trusted friends in adulthood, the damage of a tough childhood could be undone.

From Aging Well: Surprising Guideposts to a Happier Life from the Landmark Study of Adult Development:

It is not the bad things that happen to us that doom us; it is the good people who happen to us at any age that facilitate enjoyable old age ... For women, as well as for men, spouses could sometimes heal dysfunctional childhoods ... A good marriage at age 50 predicted positive aging at 80 ... After following disadvantaged Hawaiian youth for almost half a century, Emmy Werner explained that "the most salient turning points ... for most of these troubled individuals, however, were meeting a caring friend and marrying an accepting spouse."

We need love at every age. A warm childhood is a great blessing but, as with so many other things in life: "better late than never."

(To learn 5 secrets from neuroscience that will increase your attention span, click here.)

So if the study found one big thing you damn well better remember, what was it?

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