The secret to happiness isn't a great job, lots of money or a dream vacation. It's being around people who make you happy, according to a Harvard University study that compared some of the poorest men in Boston with some of the most successful to come up with the answer. 

For more than seven decades, Harvard's Grant and Glueck study kept tabs on 456 poor men living in Boston and 268 male graduates from Harvard, including John F. Kennedy, the future president of the United States. They studied blood samples, conducted brain scans and conducted self-reported surveys to reach the conclusion that intelligence and poverty weren't the ultimately deciding factors of how good a life can be.

"The clearest message that we get from this 75-year study is this: Good relationships keep us happier and healthier. Period," Robert Waldinger, director of the Harvard Study of Adult Development, told INC in an article published this week. 

In short, being in a loving relationship helps your nervous system relax, keeps your brain healthy and reduces all kinds of pain. In contrast, lonely people tend to die younger.

"It's not just the number of friends you have, and it's not whether or not you're in a committed relationship," said Waldinger. "It's the quality of your close relationships that matters."

You don't need tons of friends a huge love. A few close friendships will get the job done. "Relationships are messy and they're complicated," said Waldinger. But, "the good life is built with good relationships."

But people can't just settle for any human interactions. A relationship that improves your life involves sharing and being truly honest, the study determined. People must find love and then find "a way of coping with life that does not push love away," said George Vaillant, the Harvard psychiatrist who directed the study from 1972 to 2004.

The results of the study have been cited for years to encourage improved quality of life. It also concluded that avoiding smoking is the biggest key to aging well, while alcohol was the primary cause of divorce.