Depression runs in families, we know. But it is only very recently, and after considerable controversy and frustration, that we are beginning to know how and why. The major scientific discoveries reported last week by the Psychiatric Genomics Consortium in Nature Genetics are a hard-won breakthrough in our understanding of this very common and potentially disabling disorder.
If your parents have been depressed, the chances that you have been or will be depressed are significantly increased. The background risk of depression in the general population is about one in four – each of us has a 25% chance of becoming depressed at some point in our lives. And if your parents have been depressed, your risk jumps by a factor of three.
However, controversy has long swirled around the question of nature or nurture. Is the depressed son of a depressed mother the victim of her inadequate parenting and the emotionally chilly, unloving environment she provided during the early years of his life? Or is he depressed because he inherited her depressive genes that biologically determined his emotional fate, regardless of her parenting skills? Is it nature or nurture, genetics or environment, which explain why depression runs in families?
In the 20th century, psychiatrists ingeniously teased out some answers to these questions. For example, it was found that pairs of identical twins, with 100% identical DNA, were more likely to have similar experiences of depression than were pairs of non-identical twins, with 50% identical DNA. This indicated clearly that depression is genetically heritable. But well into the 21st century, the precise identity of the "genes for depression" remained obscure. Since 2000, there has been a sustained international research effort to discover these genes, but the field has been bedevilled by false dawns and inconsistent results.
That is why the study published last week is such a significant milestone. For the first time, scientists around the world, with leading contributions from the UK's world-class centres of psychiatric genetics research largely funded by the Medical Research Council at the University of Cardiff University, University of Edinburgh University and King's College London, have been able to combine DNA data on a large enough sample to pinpoint which locations on the genome are associated with an increased risk of depression. So we now know, with a high degree of confidence, something important about depression that we didn't know this time last year. We know that there are at least 44 genes, out of the 20,000 genes comprising the human genome, which contribute to the transmission of risk for depression from one generation to the next.
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https://www.theguardian.com/commentisfree/2018/apr/29/revolution-in-our-understaning-of-depression-will-be-life-transforming?
