How happy are your neighbors? If you don’t know the answer, you might want to find out.

Why would anyone suggest giving attention to your neighbors’ happiness? Well, other than it being nice, a happiness study suggests it might make a difference in how you feel.

That’s right, apparently happiness is contagious, like the flu but more fun. At least that is what the study, which followed a group of people for 20 years, concludes.

A cheery next-door neighbor, according to a story about the research, has more effect on your happiness than your spouse’s mood.

“Your happiness depends not just on your choices and actions, but also on the choices and actions of people you don’t even know who are one, two and three degrees removed from you,” said Dr. Nicholas A. Christakis, a physician and social scientist at Harvard Medical School and an author of the study. “There’s kind of an emotional quiet riot that occurs and takes on a life of its own, that people themselves may be unaware of. Emotions have a collective existence — they are not just an individual phenomenon.”

Emotions have a collective existence. I’m not sure exactly what that means, but it raises a lot of questions.

For example, what if you have neighbors on two or more sides? Must they all be happy in order to catch the happiness bug? What happens if only one of them is happy and the rest are sour as lemons?

Then there is the finding that it’s not only your neighbors, but those connected to your neighbors and friends who may have an effect.

Study co-author, James H. Fowler, an associate professor of political science at University of California, San Diego, said research found that “if your friend’s friend’s friend becomes happy, that has a bigger impact on you being happy than putting an extra $5,000 in your pocket.”

This comes from analyzing information on the happiness of 4,739 people and their connections with several thousand others — spouses, relatives, close friends, neighbors and co-workers — from 1983 to 2003.

So, it is not only neighbors’ happiness that is important, but also their friends and their friends’ friends. This is getting bigger than my mind can hold. (Also, I’m willing to test that $5,000 in your pocket theory if they need a volunteer.)

Think of the impact on purchasing real estate. Wouldn’t you want to know the happiness rating of a potential neighborhood? And what happens if happy neighbors move? How do you insure a bunch of grumps don’t move in and squash your happiness?

Other research experts recommend caution when looking at the results.

“It’s extremely important and interesting work,” said Daniel Kahneman, an emeritus psychologist and Nobel laureate at Princeton, who was not involved in the study. However, Kahneman said unless they replicate the findings he doesn’t accept a spouse’s happiness has less impact than a next-door neighbor.

An accompanying editorial about the two studies called them “groundbreaking,” but said “future work is needed to verify the presence and strength of these associations.”

Another important question — if happiness is contagious what about misery? Does misery not only love company, but also infect anyone living within a one mile radius?

There are so many questions and maybe it’s a bunch of bunk. After all, the story said the team previously concluded obesity and quitting smoking are socially contagious.

Still, one of the co-authors takes the findings seriously.

“This now makes me feel so much more responsible that I know that if I come home in a bad mood I’m not only affecting my wife and son but my son’s best friend or my wife’s mother,” Fowler said.

My personal reaction to the study — I really hope happiness is my neighbor. Maybe I should send over cookies as a welcome.