The Washington Post is reporting, “Happiness is contagious, spreading among friends, neighbors, siblings, and spouses like the flu.” They base their headline on a study published this week online in the BMJ.
More Information:
Nicholas Christakis, M.D., Ph.D., of Harvard University, and James Fowler, Ph.D., of the University of California-San Diego, “analyzed information on the happiness of 4,739 participants and their connections with several thousand others…from 1983 to 2003,” the New York Times adds. 
They found, for instance, that “a next-door neighbor’s joy increased one’s chance of being happy by 34 percent, but a neighbor down the block had no effect.” Meanwhile, “a friend living half a mile away was good for a 42 percent bounce, but the effect was almost half that for a friend two miles away.”
The Los Angeles Times reports, “The research is part of a growing trend to measure well-being as a crucial component of public health. Scientists have documented that people who describe themselves as happy are likely to live longer, even if they have a chronic illness.”
The researchers based this study on data “from the Framingham Heart Study, which has been running since 1948 in Framingham, Massachusetts,” Bloomberg News notes. 
The authors “defined happiness as a perfect score on the questions ‘I felt hopeful about the future,’ ‘I was happy,’ ‘I enjoyed life,’ and ‘I felt that I was just as good as other people.'” 
According to Dr. Christakis, “The Framingham data had been used before to assess depression as a risk factor for heart disease, but this was the first time researchers looked at happiness across a broad network.”
I wrote about this phenomenon in my books 10 Essentials of Highly Healthy People and God’s Design for the Highly Healthy Person. In those books, I wrote this:

I’m convinced that happiness—true happiness—is rooted in a personal relationship with our Creator. Knowing God and pleasing him result in an abiding hope. In other words, it may be impossible to have a full and balanced emotional wheel if you have a flat spiritual one. 

The writer of the Old Testament book of Ecclesiastes makes this profound statement: 

A man can do nothing better than to eat and drink and find satisfaction in his work. This too, I see, is from the hand of God, for without him, who can eat or find enjoyment? To the man who pleases him, God gives wisdom, knowledge and happiness, but to the sinner he gives the task of gathering and storing up wealth to hand it over to the one who pleases God. This too is meaningless, a chasing after the wind.

If you’re feeling a lack of happiness, or if you’re feeling hopeless, is there any hope that hope can be found? Most assuredly! 

We can see a glimpse of true hope in this ancient passage of Hebrew wisdom, for it is God who gives wisdom, knowledge, and happiness to the person who pleases him. 

Where are meaning and purpose and hope and true happiness found? According to the writer of Ecclesiastes, only in pleasing God—our Creator. 

Blaise Pascal, the French physicist and philosopher, wrote: “There is a God-shaped vacuum in the heart of every man which cannot be filled by any created thing, but only by God the Creator.”

Samuel Smiles wrote, “Hope is the companion of power, and mother of success; for who so hopes strongly has within him the gift of miracles.” 

Happiness is not only healing, as this study indicates, it is contagious. And one cannot be highly healthy without hope and happiness—which springs first and foremost from a personal relationship with God. 

The Bible tells us that “the fruit of the Spirit is love, joy, peace, patience, kindness, goodness, faithfulness, gentleness, and self control.” Therein is the root of true happiness.