A gene linked to obesity may also provide protection from major depression, say scientists. Although the gene is associated with obesity, the results were found to be independent of a person's body mass index (BMI) – a standard read-out of human body fat.
'It won't make a big difference in the day-to-day care of patients', said Dr David Meyre of McMaster University, Canada, who conducted the study. 'But, we have discovered a novel molecular basis for depression'.
To date there have only been a few discoveries of genes associated with depression (see for example BioNews 606). Researchers have now shown a gene expressed highly in the brain, called FTO, may have a role in depression. The study investigated the link between a variant of FTO associated with obesity, BMI and the risk of developing depression.
Data collected by four studies was analysed, which included information on the variant of FTO and depression state. The study participants were from numerous countries and of various ethnicities. In total 6,561 people with depression and 21,932 controls were included in the analysis.
As expected the researchers found that people with more copies of the FTO variant had a higher BMI, and that a higher BMI was associated with a small (two percent) increase in the risk of depression.
However, when analysing the relationship between depression and the FTO variant regardless of a person's BMI, they found that each copy of the variant decreased the risk of depression by eight percent. The authors state that the reduced risk of depression was 'unexpected', and the results 'must be interpreted with caution'.
Dr John Dixton of Monash University, Australia, who was not involved in the study, told ninemsn that a 'strong link' between obesity and the development of depression has already been established.
'The levels of depression get to be as high as 40 percent in those that are severely obese', he said. 'We think it's related to conditions such as diabetes, sleep disturbance, the psychological issues of being very big and the chemicals related to being severely obese. It's not as simple as a single gene'.
The authors agree, stating that 'the link between the obesity predisposing gene and depression is complex' and that other influencing factors in this association 'remain unknown'. They cautiously conclude that 'the FTO gene may have a broader role than initially thought'.
The study was published in Molecular Psychiatry.