Scientists 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.
The discovery, 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 causes serious distress to many millions of people worldwide – the World Health Organisation 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. Yet scientists have had less success in discovering genes associated with it than for any other important chronic condition.
Several studies over the past decade 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.
“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,” said Gerome Breen, lead author of the King’s study. “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.
They will then 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.
Many genes – probably more than 100 – 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, said Lefkos Middleton, Professor of Clinical Neurology at Imperial College London.
“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.