For the first time, researchers have identified specific genetic clues that might underlie susceptibility to clinical depression. The findings are the result of an international collaboration led by Jonathan Flint of WTCHG and Kenneth Kendler of Virginia Commonwealth University, together with Jun Wang of the Beijing Genomics Institute, and involving researchers throughout China.
Previous studies have failed to confirm the presence of molecular genetic markers associated with a higher risk of depression. Now, as Flint and his colleagues report in the journal Nature, they have successfully isolated individual changes in the DNA of depressed patients that appear to increase their risk.
According to the World Health Organisation, clinical depression carries the second heaviest burden of disability among all medical conditions worldwide. In the UK, between 8 and 12 per cent of the population experience depression in any year. The findings from this study could potentially lead to new treatments for the disease.
‘This report shows for the first time that genome-wide association studies – a method that has found risk genes for many important complex human disorders – can work for major depression’ says Flint. ‘With these genome-wide studies, as you identify more markers your ability to identify specific biological pathways to illness substantially improves.’
He attributes the team’s success to the carefully designed study, which collected DNA from 5,303 Chinese women with recurrent major depression from 58 hospitals throughout China. For comparison they took DNA samples from 5,337 Chinese women with no history of the disease. The study was limited to women because about 45 percent of the genetic liability to major depressive disorder is not shared between sexes.
‘It is likely that our study was successful because the patients we studied were relatively homogenous and severely ill’, says Flint.
He and Kendler hope to return to China in the near future to collect another 48,000 samples, which they expect will replicate and substantially extend the findings of the Nature study.