23andMe identifies genetic clues to the cause of depression with a massive depression study

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23andMe, the California-based company provides DNA analysis service and provides information about the genetic history of a person and a chance to learn about their DNA. Till date more than 1.2 million people have purchased gene reports from them.

In a landmark study, 23andMe along with the drug giant Pfizer have carried out a massive crowdsourced depression study using the DNA of more than 450,000 customers of 23andMe, thereby unraveling a major finding on genetic clues to the cause of depression. This study has detected 15 regions of human genomes that are linked to a higher risk of struggling with serious depression.

The reason why it has been difficult to get insights into the genetic causes of depression was because of the size of the study- it was too small a study, to detect anything significant. Ashley Winslow, a former neuroscientist at Pfizer and the current director of neurogenetics at the Orphan Disease Center at the University of Pennsylvania says “Everyone is recognizing that this is a numbers problem. It’s hard if not impossible to get to the numbers that we saw in the 23andMe study.”

A “genome-wide association study” was used, in which the DNA of many people with a disease is compared to that of healthy controls, using a computerized search. The genetic differences that often appears in sick people helps in providing the information about what genes are involved.

This gene-hunting tactic has led to several important insights into diabetes, schizophrenia, and other common diseases. However, until now, depression has remained mostly unexplored. In the past, a study in 6,000 severely depressed Chinese women identified two signals in the genome, but other surveys have failed to obtain any significant insights.

Douglas Levinson, a psychiatrist and gene researcher at Stanford University involved with the Psychiatric Genomics Consortium says “The big story is that 23andMe got us over the inflection point for depression. That is exciting. It makes us optimistic that we are finally there.”

Through its surveys, 23andMe was able to locate more than 141,000 people who said they had been diagnosed with depression. This data is 10 times more than the next-largest depression study carried out so far, says Levinson. DNA data of 337,000 customers of 23andMe who reported no depression were used as controls. This study was feasible due to the participation of half of its customers, who have agreed to allow their DNA to be used in further research and answer survey questions about their health.

Geneticists, however, believe that even larger databases are required. Taking their suggestion seriously, the US government has begun implementing plans for a million-person precision medicine database. The genetic risk for depression is infact due to hundreds of genes, each having a very small effect.

The authors of the report believe that the finding is an endorsement of 23andMe’s data. Levinson noted depression to be a perfect test case for a consumer database. Unlike other psychiatric ailments, depression is a common disease, and is no longer highly stigmatized with people willing to say they have it. Levinson says “It they tried to do it in schizophrenia or anorexia they’d probably fail. That’s the caveat here.”

 Source: MIT Review

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