Scientists say they've discovered a happiness gene that may explain why women tend to be more chipper than their male counterparts.
It's called MAOMA, or monoamine oxidase A, which, surprisingly, has also been related to negative behaviours like alcoholism, aggressiveness and antisocial behaviour, says a team of US scientists.
But in their study, the researchers found that the same, low-activity form of the gene was also associated with higher self-reported happiness in women. Results were published in the journal Progress in Neuro-Psychopharmacology & Biological Psychiatry and released this week.
Overall, while women experience higher rates of mood and anxiety disorders, they also tend to report greater life happiness than men, the study pointed out.
To investigate why this may be, scientists from the University of South Florida, Columbia University, the National Institutes of Health and the New York State Psychiatric Institute examined the role of MAOA. The gene works by regulating an enzyme which breaks down the brain's 'feel-good' chemicals like serotonin and dopamine. The low-expression version of MAOA allows larger amounts of these neurotransmitters to stay in the brain and boost mood.
A total of 345 subject participated in the study, of which 193 were women and 152 were men. DNA samples were taken to analyse for MAOA gene variation, and participants were asked to rate their levels of happiness.
Where the study becomes interesting, however, is that men who carried the same "happy" gene were no more content than those who didn't carry it.
One possible explanation is that testosterone may cancel out the positive effects of the MAOA gene, researchers theorize.
"Maybe men are happier before adolescence because their testosterone levels are lower," surmised lead author Henian Chen.
Meanwhile, authors of another study published in the Journal of Happiness Studies in 2008 found that while women may start out happier in life, men often catch up, overtaking them on the happiness scale during the later stages of life.
The main reason? Unfulfilled life goals, researchers said.