Researchers have discovered that a gene called FTO, known to be associated with obesity, keeps people away from depression.

The study challenges the perception that obese people become depressed about the way people judge them on their weight and over social and economic discrimination.

"We set out to follow a different path, starting from the hypothesis that both depression and obesity deal with brain activity. We hypothesized that obesity genes may be linked to depression," said David Meyre, senior author of the study from McMaster University.

According to the first author Dr. Zena Samaan, studies linking genes to depression have been surprisingly unsuccessful, even though previous studies have shown that people are genetically predisposed to being depressed.

Data for the study came from EpiDREAM study led by the Population Health Research Institute, which analyzed 17,200 DNA samples from participants in 21 countries. Researchers from McMaster analyzed genetic and psychiatric status of these patients.

Researchers found that FTO - gene that predisposes people to obesity - was associated with an eight per cent reduction in the risk of depression.

The study findings were confirmed by cross checking with data available from three other large-scale international studies.

"The difference of eight per cent is modest and it won't make a big difference in the day-to-day care of patients. But, we have discovered a novel molecular basis for depression," said Meyre.

Meyer added that the study is the first evidence that the obesity gene FTO actually protects the people from major depression, regardless of their weight.