As direct-to-consumer genetic testing spreads, a major concern expressed by ethicists and physicians has been whether the average person will be able to understand the results of these somewhat subtle tests. Rather than giving an answer in black and white, the tests predict whether someone has an elevated risk for developing common diseases, such as Alzheimer's. Even if consumers do understand the results, it has been unknown how they might react to news that they have a sequence of DNA that raises their risk of developing a disease.

Two new studies suggest that most patients cope easily with such negative genetic information. People who learn that they carry a high-risk genetic variant for Alzheimer's disease, called APOE4, have no greater anxiety over their long-term prospects than do those who don't know their risk, according to research published today in the New England Journal of Medicine. Another recent study of smokers revealed that those who found out that they had a lower genetic risk for developing lung cancer were just as interested in stopping smoking as those determined to be at higher cancer risk.

"The findings may help us to subdue paternalistic concerns that we have to protect people from this information," says Colleen McBride, chief of the Social and Behavioral Research Branch at the National Human Genome Research Institute, in Bethesda, MD, and senior author on the smoking study. "People given the option to take these tests can protect themselves, and they find it useful to know the results, even if the test hasn't been proven to make a difference in what they do."

In the past few years, a number of companies have sprung up to offer genetic testing directly to consumers. "Studies like this are important because we are clearly going to see testing like this make its way routinely into mainstream medicine," says Michael Christman, president of the Coriell Institute for Medical Research. Because the results of this type of testing are much more complex than the genetic tests currently used most commonly in medicine--largely single-gene testing for rare, severe disorders, such as cystic fibrosis--physicians worry about how people will react. Some have speculated that someone at high risk for neurological disease might give up on long-term relationships, or someone at low genetic risk for type 2 diabetes might indulge in a diet of doughnuts and cheeseburgers.

To date, most sociological studies of genetic testing have focused on rare inherited diseases rather than on more common ones, such as Alzheimer's. Robert Green and his colleagues at Boston University are among just a handful of researchers examining this issue: Green's team has spent the past decade studying the impact of genetic testing for APOE4, which raises the risk of developing Alzheimer's disease threefold in those who inherit one copy and tenfold in those who have two copies. No proven treatments exist to reduce Alzheimer's risk in APOE4 carriers, and testing for the risk variant is not currently recommended. But surveys indicate that 15 percent of primary-care physicians who treat patients with Alzheimer's have already been asked about the test.

In the newly published study, Green and his colleagues offered APOE4 testing to adult children of people with Alzheimer's disease and then revealed the results to half of the group. The team found that people clearly understood their results, and that six weeks after learning them, those who were told that they had the high-risk variant seemed more stressed than the other participants. But that spike in anxiety had faded by the time participants were tested again both six months and one year afterward.

"We were astounded by how many people wanted to know: more than 20 percent wanted to receive it," says Green. "Even though patients clearly understood there was nothing they could do to stave off the disease, they had nonmedical reasons to learn about it: to prepare their children, to think about the longevity of careers."