How Far Are We From a Genetic Test for ADHD?

It’s hard to manage ADHD if you don’t know you have it. Lack of diagnosis is a major obstacle to effective ADHD treatment.

According to one study, people with ADHD experience symptoms for an average of 17 years before they receive treatment. And that’s assuming they ever do get diagnosed.

No wonder, then, that a main area of ADHD research has been looking for more accurate ways to diagnose people with ADHD. While questionnaires and screening tests have proven indispensable tools for spotting people with symptoms of ADHD, researchers are always working to improve the diagnostic methods mental health professionals have to work with.

Perhaps the holy grail would be a genetic test for ADHD. Already, it’s possible to send in a saliva sample and find out your status for a multitude of genetic traits and conditions using direct-to-consumer DNA services like 23andme. Imagine if you could order an equally convenient test to find out your risk for ADHD!

In theory, that dream is sound. We know that ADHD is highly heritable, with research suggesting that 70-80 percent of whether you have ADHD is down to your genes.

In practice, though, how far are we from actually having that test?

A new meta-analysis, or “study of studies,” from psychology and health researchers at University of Wisconsin explores that question. The researchers surveyed genetic tests described in previous research for calculating someone’s ADHD risk.

These particular tests are known as polygenic risk scores. They’re polygenic because ADHD isn’t a disorder where you either have “the ADHD gene” or you don’t – rather, genetic risk for ADHD seems to be determined by many, many different genes that each have a small influence. And they’re risk scores because, well, they try to put a number on someone’s risk for having ADHD.

So the researchers posed a straightforward question: how good are polygenic risk scores at actually predicting whether someone has ADHD?

They found that previously published methods for calculating polygenic risk scores tended to predict about 3.5-4 percent of the variation in actual ADHD traits.

From a scientific perspective, 4 percent is an accomplishment. It means we’re making progress on understanding what genes contribute to ADHD.

But from a practical perspective, it means not to hold your breath on a genetic test for ADHD. Knowing that someone is a couple of percentage points more likely to have ADHD isn’t vastly useful to a mental health professional making a diagnosis, so there’s clearly a lot more research that needs to be done before genetic testing can improve the current ADHD diagnostic process.

It’s worth noting that the 4 percent is for state-of-the-art methods used by scientists in research settings, so the genetic tests available to consumers right now tend to be even less informative. Most direct-to-consumer genetic testing companies, for example, only look at a handful of points in the genome, and the results they report may be unreliable.

None of which is to say that research into the genetics of ADHD hasn’t made real progress. The fact that we can now predict even 4 percent of the variation in someone’s ADHD symptoms purely based on their genes is a scientific accomplishment. Still, there’s plenty of more science that’s going to need to happen before that progress can translate into game-changing clinical tools.

Image: Flickr/MIKI Yoshihito

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