Opinion: The Trouble With Home DNA Tests

(Dec. 20) -- Individually wrapped praline swirls. "Excellent." Funky striped knee-length socks. "Nice touch." And, right at the bottom of the stocking, a DNA test. "Oh. Santa, you really shouldn't have. ..."

I mean, you really shouldn't have.

Believe it or not, personal genetic tests -- which promise to reveal risks of future health conditions from pancreatic cancer to heart attack -- are being promoted as wonderful Christmas gifts this year.

One U.S.-based company, 23andMe, is selling them at a knockdown $99 until Dec. 25. The website of another, DeCODEme, quotes a buyer saying this gift will make their children's "whole future happier and healthier."

Happier? I'd like to speak to these kids.

What about the worry, the stress, the anxiety? Science today is confirming what professional athletes, artists and Buddhist monks have always known: Happiness comes from living in the now. In November, Harvard psychologists published evidence that thinking ahead makes people miserable. "The present moment is filled with joy and happiness," writes Buddhist monk and peace activist Thich Nhat Hanh. "If you are attentive, you will see it."

How can anyone breathe deeply and enjoy today, if they are fretting about LRRK2 G2019S mutations that may, in 2034, lead to Parkinson's? How will folks enjoy their kid's crazy laughter and passionate gobbling now, if they know they have higher risks of schizophrenia and obesity in later life?

And what are these risks anyway? The predictive value of direct-to-consumer tests is low. You may have "slightly higher odds" of bladder cancer. That means about 1.2 times the risk. You may learn that 19 in every 10,000 males of European ancestry with your genotype variants develop multiple sclerosis in their lifetime. Compare that to an average of 23 in every 10,000 males. What can you possibly do with this information?

"Make better health decisions by learning your genetic risks." That's the sales pitch. More than a third of customers surveyed by Johns Hopkins University said they had changed their diets after taking genetic tests. I think I would too. When I feel fat, I eat toffee-pecan ice cream. If I discovered "slightly higher odds" of type 2 diabetes, I might buy a pie shop.

Of course, living in the present has always been tough for humans. Witness the almanacs, clairvoyants, oracles, prophets and visions of the afterlife. Genetics is just the latest player in the futures game.

But what a detailed and convincing tale it tells. In November alone, scientists announced genetic markers for alcohol tolerance, body mass index, HIV, early menopause and Hodgkin's lymphoma. Which means we'll no doubt soon be able to spit in a tube and test for these conditions, too.

Genetic information is changing the world -- improving health, extending lives. One example: Preimplantation genetic diagnosis is helping IVF patients screen out embryos with chromosomal abnormalities, reducing miscarriage and painful genetic disease. Another: Genetically modified sterile mosquitoes promise to tackle dengue fever globally (even if a trial in the Cayman Islands has caused some surprises).

But do people know what they're getting into when they buy a personal genetic test online?

Genetic information is complex, involving probabilities, not certainties. Environment, diet, lifestyle -- these all cause disease too. The American Society of Human Genetics said in 2007 that direct-to-consumer genetic tests put consumers at risk. Last month, Germany's national academy of sciences called for a ban.

Personally, I just don't need anything else to stress about. Don't bring me one, Santa. Please.

Heather Walmsley is a freelance writer and a research associate at Concordia University in Montreal, with a Ph.D. in genetics and society.