Study: Depression, Autism And Schizophrenia Share Genetic Links

Attention deficit hyperactivity disorder, major depression, bipolar disorder and schizophrenia may be linked by common genetic risk factors, according to a new study published in The Lancet. Audie Cornish speaks with study author Jordan Smoller of Harvard Medical School.

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AUDIE CORNISH, HOST:

Scientists have known for some time that genes play a role in disorders like major depression, bipolar disorder, autism, schizophrenia and ADHD. But a major new study published in the journal Lancet suggests that those five disorders may actually share some of the same genetic links. The study analyzed the DNA of more than 60,000 people around the world. Jordan Smoller is a professor of psychiatry at Massachusetts General Hospital and Harvard Medical School. And he helped lead the study. I asked him what the study set out to find.

JORDAN SMOLLER: The big question was whether we would be able to see any specific genetic variations - that is variations in DNA - that were linked to not just one disorder but to all five of these disorders that we think of as quite different.

CORNISH: So what did you actually find?

SMOLLER: We did, in fact, find several specific genetic variations that seemed to increase the risk for all five of these different disorders. And interestingly, a couple of them seemed to cluster in what we call calcium channel signaling genes. And these are genes that are important in how brain cells communicate.

CORNISH: When you say genetic variations, does this mean that certain people might be predisposed to the development of these disorders? Is that where this is leading?

SMOLLER: Well, we do think that genetic variation - that is differences in DNA sequence - contribute to some vulnerability to these disorders. They are not destiny - that is, it doesn't account for all of the risk. But it turns out that all the psychiatric disorders and neuropsychiatric disorders that have been studied so far have demonstrated some genetic component. And we're just beginning to see research that is identifying the specific genes that may be involved.

CORNISH: So what's significant about these findings? I mean, why is this important?

SMOLLER: Well, there are a few things, I think. One is that it suggests that there may be some degree of shared biology among these very different disorders that affect the brain. And the other is that it gives us some new leads to follow up - that is, to chase down some of what these genes may be doing. How is it that they have such broad effects? And can we, in fact, use that information to develop new and better ways to help people?

CORNISH: Let's get into that a little bit more. I mean, as a psychiatrist, what could this mean for the day-to-day work of people like yourself? I mean, are we talking about testing tools or about the treatment for these mental disorders?

SMOLLER: Well, that's a good question and in fact it's important to emphasize that we are not talking about testing tools here. These are actually a small fraction, we think, of the genetic component of each of these disorders. What it does do is point us in the direction of novel kinds of biological clues that could then be targets for treatment. And so, this then begins a process of looking for ways to translate that information into something that might actually be helpful to folks.

CORNISH: So now that you have this information, do you think it will change how people think or treat these disorders?

SMOLLER: Well, one of the interesting things is that our current system of classifying psychiatric disorders is really just based on symptoms rather than causes. And I think studies like this one, in conjunction with studies of brain imaging and behavior and so on, may help us begin to look at these disorders in a different way, to begin to understand them and maybe ultimately diagnose them based on their root causes rather than their symptoms.

CORNISH: Jordan Smoller, thank you so much for explaining it to us.

SMOLLER: Thanks so much for having me.

CORNISH: Jordan Smoller, he's professor of psychiatry at Massachusetts General Hospital and Harvard Medical School.

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