There’s a DNA test that can determine which antidepressants are right for you

The test will determine which antidepressant or anti-psychotic drug will work best for a particular patient, allowing them to circumvent the side effects of taking the wrong drug.
The test will determine which antidepressant or anti-psychotic drug will work best for a particular patient, allowing them to circumvent the side effects of taking the wrong drug. Sara Dell'Antoglietta

When it comes to mental illness, medication is often a key component of treatment. But finding the right type and dose can be a time-consuming, costly and sometimes dangerous game of trial and error.

In response, researchers at the Centre for Addiction and Mental Health (CAMH) in Toronto are conducting the Impact Study that analyzes individual patients’ DNA to determine the most effective medication for their genetic makeup. They say that the results will speed up treatment while minimizing side effects for patients.

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“So far, we’ve tested 9,000 people [since starting the study in 2013], and our analysis has shown a 27 per cent reduction in the severity of depression symptoms in patients whose doctors have followed the guidance,” says Dr. James Kennedy, head of the Tanenbaum Centre for Pharmacogenetics at CAMH. “We also conducted a similar study to treat anxiety disorders and it showed [similar results].”
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The test involves taking a swab of saliva from a patient’s mouth and sending it to a lab to be tested for 10 genes. Of the genes tested, eight determine how the liver will break down a particular drug — if it works too fast, it won’t make its way to the brain. If it works too slow, it can accumulate in the bloodstream and create toxicity. The other two genes determine how the drug will affect the brain.

Once the lab has analyzed the results, they are sent to the patient’s physician, who will be able to deduce what kind of drug to select for treatment. The test covers about 35 of the most commonly used antidepressant and antipsychotic medications.

“It’s a nice, quick, easy and user-friendly way for doctors to pick medicine for their patients,” Kennedy says.

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The clinical trials will continue for another year, at which point they will need to be analyzed and then sent to the Ministry of Health, where it will be determined if it falls under the jurisdiction of the health-care program. Kennedy says the results won’t be presented until early 2019.

A similar test is used in the U.S. right now, and he says studies have shown that the testing has saved patients up to $5,000 (in one Minnesota study).

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“Our primitive data shows a range of savings from $1,500 to $2,000 over the 12 months following the test. It could revolutionize the way doctors write prescriptions,” Kennedy says.

But how will the pharmaceutical companies feel about the possibility of losing out on sales from trial-and-error tactics that inevitably sell more drugs?

“This runs counter to pharmaceutical companies’ old style of creating ‘blockbuster drugs'” — a term used for medications like Prozac that were prescribed in sweeping numbers in the late 1980s. “But they’ve been monitoring these studies for years and they see the writing on the wall that this is more intelligent prescribing.”

He predicts that the drug companies will adapt by partnering with some type of genetic testing company that will allow them to market a “smart” drug.

“If they put a new drug on the market, the FDA will likely require data on how their drug behaves in the face of this genetic testing. They’ll have to generate the data, and will develop a marketing plan that will say their drugs are more intelligently prescribed.”

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Sun Life Financial partnered with CAMH’s study in August for a pilot project with the goal of curbing the $6 billion in lost productivity due to mental health issues.

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“Mental health is a key area of focus for us as it’s a large driver behind absence from work,” says Marilee Mark, vice-president of integrated health solutions, group benefits at Sun Life. “Often people will try one drug and it won’t work and they’ll experience side effects, at which point their doctor will put them on a second and third drug. Then you run the risk of the patient not taking treatment at all. It’s something you want to intervene with as early as possible.”