The figure, which comes from a 2003 paper published in the prestigious journal Science, shows that the risk of depression among people who have experienced stressful life events becomes much greater if they also possess a certain version of a certain gene. This landmark study, in the midst of an endless nature-nurture debate, was evidence that not only were both genetic and environmental factors important, the two worlds actually depended on each other. This demonstration of what was called a “gene-environment interaction” became a cornerstone principle in our understanding of how behavior, both typical and atypical, develops……
…. A new study, now, throws all of this into question……
….But a study published last month in the American Journal of Psychiatry has dealt a major blow to the entire candidate gene world. Using samples of up to nearly half a million people, the researchers decided to try and replicate the results of dozens of previously published links (which were often based on much smaller samples) between 18 particular candidate genes and depression, either on their own or in interaction with environmental factors such as early abuse or poverty. What they found was essentially nothing, and the authors argued that these particular genes are “no more associated with depression… than genes chosen at random.”….
To be clear, it is also important to point out what this study does not mean. First and foremost, it does not mean that there isn’t a genetic basis to depression, just that it more likely involves a much larger number of genes, each of which alone has a very small effect. Scientific evidence from many other sources, like twin studies, still point quite convincingly to the important—although certainly not overpowering—role of genetics in the development of depression and most other psychiatric conditions as well. The study also doesn’t shoot down the gene-environment interaction hypothesis either, it just again makes it a bit more complicated. Finally, it is important to note that the study was focused on depression and there are examples in other conditions, from cystic fibrosis to breast cancer, where single genes can play large roles in the development of the illness.
One area that will certainly get some additional scrutiny is companies charging hundreds of dollars to tell you about your risk for depression based on your status of many of the very same genes that were debunked in this study. Whether some insurance companies will still be willing to cover these tests is also very much in question.
2019-06-21