Adding to the complicated and often elusive search for happiness, a new study finds that a gene may play an important role – if you’re a woman. The study adds to the discussion of how genes and the environment interact to create our emotional experience and risk for mental health problems. It also suggests these interactions may differ by gender.

The researchers followed 193 women and 152 men who were part a long-term mental health study. They analyzed the genomes of the participants and asked detailed questions about their emotional, mental, and physical health.

They found that a key gene, known as monoamine oxidase A (MAOA) was a strong predictor of happiness, even after other factors like age, education, and income were controlled for. The MAOA gene directs the activity of a compound that breaks down the “feel good” neurotransmitters serotonin and dopamine. People with lower levels of the gene would have higher levels of these important brain chemicals, which are the same neurotransmitters targeted by antidepressant medications like Zoloft and Prozac. The researchers found that people with the “low-expression type of MAOA” were happier over all, and the more copies of the gene the participants had, the happier they were.

But the really interesting finding was that this association was only seen in women: Men’s happiness did not seem to vary along with the type of MAOA gene they had. The team suggests that this may have to do with the fact that men have more testosterone, which they say could effectively cancel out the effect of the gene, particularly as men age and testosterone rises. "Maybe men are happier before adolescence because their testosterone levels are lower," suggested author Henian Chen in a news release.

Even stranger is the fact that previously the gene was dubbed the “warrior gene,” because of its known links with traits like aggression and addiction in women. "This is the first happiness gene for women," said Chen. "I was surprised by the result, because low expression of MAOA has been related to some negative outcomes like alcoholism, aggressiveness and antisocial behavior... but, at least for women, our study points to a brighter side of this gene."

Clearly more research will be needed to sort out all the effects of the gene. The study adds some good evidence to the idea that a particular gene can help influence more than a single aspect of behavior or mood.It also suggests a new perspective about happiness, in addition to how mental health problems originate. "Certainly it could be argued,” adds Chen, “that how well-being is enhanced deserves at least as much attention as how (mental) disorders arise; however, such knowledge remains limited." Since women suffer from anxiety disorders and mood disorders like depression more than men, the study may raise more questions than it answers.

Chen directs the Biostatistics Core at the University of South Florida Health Morsani College of Medicine's Clinical and Translational Sciences Institute. The study was published in the journal Progress in Neuro-Psychopharmacology & Biological Psychiatry.