The study was huge: Researchers took the DNA of over 75,000 people who reported being clinically diagnosed with depression and compared it with more than 230,000 customers who reported no such diagnosis.
The 15 regions in the scrutinized DNA are the first to be linked to major depression in people of European descent. A previous study looking at over 10,000 people of Han Chinese ancestry found two such regions, but those are insignificant in people whose ancestors are from Europe.
This type of DNA analysis does not usually find the exact gene or mutation involved in a disease or condition, but it does narrow down considerably the areas in which to look. The 23andMe research will allow scientists to study a handful of locations from different DNA regions, instead of looking at all 20,000 human genes.
Because depression is so complicated genetically, the discovery is unlikely to prove useful as a predictive tool. Meaning, the research won’t be turned into a genetic test anytime soon. But what it can do is give scientists a deeper understanding of how major depression works.
This is becoming a common theme in genetic studies of complex diseases like major depression, type 2 diabetes and heart disease. Rather than leading to predictive genetic tests, the studies are bringing a better understanding of what causes the illness, opening up new approaches to treatment.
A Combo of Genes
In the U.S., an estimated 15.7 million adults aged 18 or older have suffered at least one major depressive episode in the past year, according to the National Institute of Mental Health.
Over the last 70 years, scientists have used twin, family and adoption studies to figure out that the risk of experiencing major depression is roughly half genetic — somewhere around 40-50 percent — while the rest is due to environmental factors, such as emotional abuse or neglect.
Because we have studied depression for so long, you might think we would have uncovered the guilty gene by now. And we probably would have if there were a single culprit.
But it turns out it’s the combination of many different genes working in concert that creates someone’s risk for the disorder. Thus, two people suffering from major depression may have acquired it for completely different genetic reasons. Add to that all kinds of different environmental factors, and you start to get a feel for what a daunting task homing in on the exact causes of depression are.
The 23andMe study, however, could at least bring us closer.
23andMe is a consumer genetics company that analyzes your DNA and reports back on your health and ancestry. To date it has accumulated data from over one million of its customers, 850,000 of whom have given the company permission to use their genetic profile for research.
This database, combined with participants’ self reporting of health conditions like depression, is one of the largest repository of individuals’ genetic data in the world. Such a large sample allows scientists to detect patterns that often remain hidden when analyzing a smaller number of participants.
Corporations and universities are ponying up to access this trove. In 2015 it was reported that 14 universities and companies, including heavy hitters like Genentech and Pfizer, had signed up for access.
Companies like 23andMe have sometimes been criticized for what detractors would call an exploitation of people’s genetic data for commercial purposes.
But if the collaborations do lead to new treatments for devastating diseases, some of that criticism may go by the wayside.