The stereotype of the jolly overweight person may not be too far off the mark.

According to new research published Tuesday, there is evidence that the major genetic contributor to obesity is linked with a reduction in the risk of depression.

Scientists at McMaster University in Hamilton, Ont., found that the gene FTO is associated with an 8% reduction in the risk of depression, making it a happy gene in addition to an obesity gene.

"The difference of 8% is modest and it won't make a big difference in the day-to-day care of patients," David Meyre, senior author of the study, said in a release. "But, we have discovered a novel molecular basis for depression."

The study challenges the commonly-held belief about the connection between obesity and depression -- that obese people get depressed about their appearance, and that depressed people may lead less active lifestyles that cause them to become obese.

Beginning with a hypothesis that both obesity and depression have to do with brain activity and that obesity genes could be linked to depression, the researchers examined the genetic and psychiatric status of patients already enrolled in another study that had analyzed 17,200 DNA samples from people in 21 countries.

Researchers found the link between the FTO gene and the 8% reduction in the risk of depression and analyzed the genetic status of patients in three other large international studies to confirm their findings.
The study is published in the journal Molecular Psychiatry.