Genetic tests for psychiatric disorders are emerging


Genetic tests raise the potential of misunderstanding, according to Andrea Patenaude, Ph.D., associate professor at Harvard Medical School. (photo by Tom Croke)

By Ami Albernaz

Given the steady progress scientists have made in decoding the human genome, it is perhaps not surprising that tests for illnesses based on these advances have closely followed. Tests claiming to help predict Alzheimer's and cancer risk are already on the market, and now, tests meant to reveal a person's vulnerability to certain psychiatric disorders are emerging.

A California company called Psynomics has released a test for the genetic markers of bipolar disorder and a test to predict patient responses to serotonin-based drugs. A Kentucky company called SureGene is expected to release a schizophrenia test next year.

Yet the prospect of these tests, at a time when the role of genes in psychiatric illnesses are not fully understood, is leading some psychologists and psychiatrists to question if the tests are too premature.

"There's no question that most psychiatric disorders have significant genetic components," says David Fassler, M.D., a clinical professor of psychiatry at the University of Vermont. "I also believe that genetic testing will eventually prove to be a helpful component of a comprehensive evaluation….I'm concerned that some of the tests are clearly promising more than they can deliver, at least based on the current science."

Psynomics' bipolar test, the first of its kind, was developed by a prominent University of California-San Diego psychiatric geneticist and is available over the Internet for $399. It tests for two mutations of a gene known as GRK3 that were found to be associated with bipolar disorder. In research on hundreds of families, some affected and some unaffected by the illness, one of the mutations appeared in one percent of individuals without the illness and three percent of those with it. The second mutation showed up in five percent of those without bipolar and 15 percent of those with it.

The question of interpreting the numbers arises. With many genes likely involved in a psychiatric disorder, "any individual test is likely to explain a very small proportion of risk," says Jordan Smoller, M.D., a psychiatrist at Massachusetts General Hospital and a principal investigator in the hospital's Center for Human Genetic Research. The Psynomics Web site states that individuals with either of the genetic mutations are three times more likely to have bipolar disorder than people without them.

"The numbers could sound very different if they're presented as a relative risk, as opposed to absolute risk," Smoller says.

Those behind the bipolar test and other forthcoming psychiatric tests say that even if the science is not yet perfect, patients have the right to know if they have a genetic make-up associated with a particular illness. The Psynomics test is marketed to people who have bipolar symptoms and those ordering the test must provide the name of a doctor to whom the results are sent. (Psynomics did not return repeated calls for comment.)

Yet these conditions do not address larger concerns some psychologists have about genetic testing. Even for illnesses for which the role of genes is better understood, grappling with the results of genetic tests and knowing how to talk to future generations about risk are difficult matters, says Andrea Patenaude, Ph.D., associate professor of psychology at Harvard Medical School and author of the 2005 book "Genetic Testing for Cancer: Psychological Approaches to Helping Patients and Families."

"I fear that there's a great deal of harm that can come from trying to sell genetic tests," says Patenaude, who has researched the impact of genetic counseling for cancer susceptibility. "Even with single-gene disorders, there's a large potential for misunderstanding. For disorders that are not single-gene, the potential is huge… I also fear that these tests now, before we have a better understanding [of the genes involved in psychiatric disorders], will bias people against the value of genetics. Someday, when we finally have a good test, people might have attitudes against it."

Given market forces and the ongoing work in decoding genes, though, genetic tests for psychiatric disorders might be here to stay. At Simmons College in Boston, Gerald Koocher, Ph.D., dean of the School for Health Studies, helped develop a certificate program to help equip health professionals to deal with what he calls "gen angst." The program, with courses including Fundamentals of Human Genetics, Overview of Genetic Counseling and Ethical, Legal, Social Issues in the Provision of Genetic Services, is designed to help practitioners feel more confident in using data from genetic tests.

Besides competence of the practitioner interpreting the test results, Koocher sees access, privacy and validity of genetic tests as issues of which to be mindful.

"There's a lot of ways a person can become seriously depressed or agitated, with no genetic basis at all," he says. "While there might be a genetic predisposition, it doesn't tell the whole story."

Genetic tests for psychiatric disorders are emerging (June 2008 Issue)

Genetic tests for psychiatric disorders are emerging
(June 2008 Issue)