5 research-backed lessons on what makes a happy life

Ever wonder what it would be like to be able to look at people's entire adult lives? Not asking older people to remember, but starting with them as teenagers and tracking their health and well-being until they die? We've been lucky enough to do this for the past 78 years, starting in the late 1930s and early '40s with a group of men who agreed to be part of one of the longest studies of adult life ever done.

The Harvard Study of Adult Development has tracked the lives of 724 men from the time they were teenagers into old age — 268 Harvard College sophomores, and 456 boys from Boston's inner city. Using questionnaires, interviews, medical records, and scans of blood and brains, we've monitored their physical and mental health, work lives, friendships, and romances.

Here are five of the big lessons we've learned about what contributes to a good life.

Lesson 1: Happy childhoods matter

Having warm relationships with parents in childhood predicts that you will have warmer and more secure relationships with those closest to you in adulthood. We found that warm childhoods reached across decades to predict more secure relationships with spouses at age 80. A close relationship with at least one sibling in childhood predicts that people are less likely to become depressed by age 50. And warmer childhood relationships predict better physical health in adulthood all the way into old age.

Lesson 2: Fostering the welfare of the next generation can ease the sting of difficult childhoods

People who grow up in difficult childhood environments (chaotic families, economic uncertainty) grow old less happily than those who have more fortunate childhoods. But by the time these people reach middle age (ages 50 to 65), those who mentor the next generation — guiding younger adults at home or at work — are happier and better adjusted than those who do not. The kind of maturation needed to nurture younger people also seems to reduce some of the sting of growing up disadvantaged.

Lesson 3: Coping effectively with stress has lifelong benefits

We all have habitual ways of managing stress and relieving anxiety. Some people tend to ignore uncomfortable facts, while others tend to face difficult issues and deal with what is unpleasant. For example, someone who is angry at his boss might "forget about it" but start missing important work deadlines. Alternatively, he might find a way to take up his concerns directly with that boss. We found that the people who cope with stress by engaging more directly with reality rather than pushing it away have better relationships with others. This coping style makes it easier for others to deal with them, which in turn makes people want to help them. They end up having better relationships and more social support, and this predicts healthier aging in your 60s and 70s. People who use these more adaptive coping mechanisms in middle age also end up with brains that stay sharper longer.

Lesson 4: Breaking bad habits earlier in life makes a difference

Watching people's smoking habits across adulthood, those who quit earlier are less likely to develop lung disease as they grow old. They are also more likely to live longer than people who do not quit smoking or who quit later in life. Our findings differ from some studies that find no change in risk of disease and death once you're tobacco-free for 15 years or more. Getting off the couch and starting to exercise earlier in life predicts that you'll stay healthy longer in life, that your brain will stay sharper, and even that your immune system will be stronger.

Lesson 5: Time with others makes us happier

Looking back on their lives, people most often report their time with others as the most meaningful part of life, and what they're proudest of. Time with other people makes us happier on a day-to-day basis, and time with a close partner buffers us against the mood dips that come with increased physical pain.

You can learn more about the study and our research at www.robertwaldinger.com and www.adultdevelopmentstudy.org. We are now studying the children of these men. Almost 1,300 of these second-generation baby boomers are participating in our study, and we hope to know more about what helps people thrive across generations.

Stay tuned.