Christmas is a happy time, or so it’s said. Chestnuts roast on an open fire. Silver bells ring-a-ling as shoppers rush home with their treasures. Tiny tots with eyes all aglow help to make the season bright.

It’s true for most of us, but not for all. Happiness can be a veneer at Christmas. While it’s a misconception that suicides and psychiatric admissions soar during the holidays, the season does strike a blue note for many. “The general mood for individuals may worsen,” concludes a 2011 study published in the journal Innovations in Clinical Neuroscience.

Indeed, the lonely may get lonelier as Christmas approaches. The poor may feel poorer. Dysfunctional families may spin out of control. Stress runs high, after all. Traffic is heavy. Patience wears thin. Cards don’t get written. Presents don’t get wrapped. Christmas is hard on perfectionists who don’t understand that they’re not Martha Stewart.

Christmas also leads us wistfully to ponder the longitude of our lives. We look at old photos. Forty years have gone by in a flash. We long for the touch and the voices of lost loved ones. We ache for those who are far away and can’t make it home. We feel helpless and vulnerable to the cruel illnesses that descend on our friends. We feel only human.

Happiness, as it happens, is not doled out evenly or equitably. Surveys name Norway as the world’s happiest country, although surely Norwegians would never show it or tell anyone about it. The Swiss, Canadians, Swedes and New Zealanders round out the happiest top five. (Americans rank 11th.) Minnesota, meanwhile, rates as the nation’s third-happiest state, just behind Hawaii and Colorado, according to another recent study.

As it turns out, social scientists love to study happiness — and to demystify it. They’ve tried their best to take the happy out of happiness by renaming it SWB — subjective well-being. Americans, it seems, now have the right to life, liberty and the pursuit of subjective well-being.

But here’s the surprising thing: Nearly half of an average person’s happiness is inherited. This is according to a survey of the social-science literature by Arthur C. Brooks, who heads the American Enterprise Institute and who wrote about happiness recently in the New York Times. Brooks’ estimate was based partly on the University of Minnesota’s groundbreaking research on identical twins growing up in separate environments.

Aside from genetics, he claims that another third or more of our happiness comes from how we experience transitory circumstances. Our mood might be buoyed by a delicious meal, for example, or an exceptional concert, or a good parking spot. That leaves maybe 12 or 15 percent of happiness that we can actually control. And here social science offers four main ingredients that can tip the scale toward a happy life: faith, family, community and work. If you can squeeze the maximum meaning out of those, well, you’re on the way to a happy life.

Hanging around with happy people might help, too, researchers have found. They’ve even tried to sort out whether happiness leads to success — or whether it’s success that makes people happy. The answer appears to be both. Happy people tend to succeed, yes. But the happiest countries (and states) tend also to be those with relative affluence and the fewest social problems.

History’s great religions and philosophies have, of course, also tackled the happiness question, coming to various conclusions: that happiness comes only in an afterlife, or that serving others is the key to bliss, or that reaching a state of everlasting peace by contemplating “divine things” is the ultimate path. In this busy season, there’s one other suggestion to consider: Instead of obsessing on the past or the future, embrace the moment as best you can.