Researchers have for the first time confirmed a specific genetic link to depression, according to new evidence published in the American Journal of Psychiatry on Monday. This finding was made independently by research teams in the UK and US, is expected to lead to a better biological understanding of the condition and eventually to more effective antidepressants.
Depression affects millions worldwide. The World Health Organization lists it as the fourth leading cause of disability and disease – and the way it runs in families demonstrates genetic as well as environmental causes. Up to one in five Britons will suffer from depression at some point during their lives. Although it is often triggered by traumatic events - such as grief, redundancy or divorce - scientists have long known that certain people are more susceptible. Yet scientists have had less success in discovering genes associated with it than for any other important chronic condition. Depression is forecast to be the highest disease burden by 2020.
There have been previous studies over the past decade that have claimed to link particular genes with depression but these are inconsistent and none has been confirmed by other research. What makes the latest evidence more compelling than previous findings is that it was discovered by two separate studies: one on 800 families with recurrent depression, led by King’s College London, and a smaller programme of 100 families, led by Washington University, St Louis.
Gerome Breen, lead author of the King’s study said, “In a large number of families where two or more members have depression we found robust evidence that a region [of chromosome 3] called 3p25-26 is strongly linked to the disorder… These findings are truly exciting as possibly for the first time we have found a genetic locus for depression. “The stretch of chromosome 3 associated with depression includes 40 of the 20,000 or so human genes. Intensive investigation over the next year is likely to pin down the gene responsible, the scientists say. For the next step they will investigate the precise biochemical role of the gene, which may be the basis for designing more effective antidepressants – though the pharmaceutical development process takes so long that new drugs could not be available in less than 10 years. The drugs available today fail to produce a sustained mood improvement in a substantial minority of patients.
According to Lefkos Middleton, Professor of Clinical Neurology at Imperial College London, probably more than 100 genes contribute to a greater or lesser extent to depression. But unlocking the mechanism of just one, even if it is responsible directly for only a small part of the genetic risk, could make an important contribution to understanding the disease. “We are just beginning to make our way through the maze of influences on depression, and this is an important step toward understanding what may be happening at the genetic and molecular levels,” added Michele Pergadia, lead author of the Washington University study
Marjorie Wallace, chief executive of the mental health charity Sane, said, “It is very exciting that there seems to be progress finding the gene involved in some people developing depression. However, we are still some distance from identifying the “culprit” gene.”
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