Researchers at McMaster University in Ontario are bucking the common perception that obesity and depression go hand-in-hand. They have discovered that a gene known as the FTO gene can be described as both an obesity gene and a happiness gene.
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Depression & genetics
Although depression is often said to run in families, very few genetic links to depression have been documented. The only existing connection was based on family studies of twins and siblings that indicated a 40 percent genetic causality for depression.
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A separate 2010 study lent credence to current popular perceptions that obese people become depressed due to the sometimes harsh physical realities of being overweight, combined with institutionalized social discrimination against the obese. Another notion is that depressed individuals become obese as a result of apathetic inactivity and poor eating habits. But the new genetic link from the McMaster Study runs counter to these notions.
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The McMaster Study
Researchers wanted to get to the root of how depression and obesity were linked, beginning with brain activity. They studied the genetic and psychiatric states of subjects enrolled in the “EpiDREAM” study directed by the Population Health Research Institute, which analyzed 17,200 DNA samples from participants in 21 countries. Within this group, researchers found that the obesity gene was associated with an eight percent reduction in the risk of depression. They bolstered this finding by examining the genetic status of patients in three additional prominent international studies. This was the first evidence to link the FTO obesity gene with protection against major depression, independent of its effect on body mass index.
The FTO Gene
The FTO gene is believed to be a major genetic contributor to obesity in spite of its association with an eight percent reduction in the risk of depression. David Meyre, an associate professor in clinical epidemiology and biostatistics at McMaster University’s Michael G. DeGroote School of Medicine, commented that “the difference of eight percent 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 of depression. “
Not all obese people have this deviation of the FTO gene. But for those who do, depression is less likely to be the cause. With more than one-third of American adults considered obese, it’s important to consider new approaches to achieving health and happiness – for example, weight-related despair may only lead to more weight gain. Additionally, it must be stressed that the causes of depression are still very much a mystery. Scientists are still researching a variety of potential sources including brain chemistry, brain circuitry, and genetics – all of which are promising approaches to treating mental illness. But exploring the genetic influences for and against depression will be a factor in eventually curing this illness.
"The protective effect of the obesity-associated rs9939609 A variant in fat mass- and obesity-associated gene on depression"
Z Samaan, S Anand, X Zhang, D Desai, M Rivera, G Pare, L Thabane, C Xie, H Gerstein, J C Engert, I Craig, S Cohen-Woods, V Mohan, R Diaz, X Wang, L Liu, T Corre, M Preisig, Z Kutalik, S Bergmann, P Vollenweider, G Waeber, S Yusuf and D Meyre
Molecular Psychiatry, November 2012, doi: 10.1038/mp.2012.160
Published On: December 17, 2012