Being told you have a genetic predisposition to alcoholism could make you feel you have less control over your drinking, a new study suggests.

The unique study adds to growing concern about the potential perils of direct-to-consumer genetic tests.

Alcoholism has been linked to a number of genes as well as environmental factors. (Michael Vosburg/The Forum/Associated Press)

Psychologist Ilan Dar-Nimrod from the University of Sydney and colleagues report their findings in the journal Genetics in Medicine.

He says the latest findings show how genetic information has the power to change a person's emotional state, behaviour and attitudes.

"We have about 1,600 genetic tests available now," Dar-Nimrod tells the Australian Broadcasting Corporation. "We should have better knowledge about how to communicate these results in a manner that doesn't create harm."

He says for a few genetic-related diseases, having a particular gene means you will definitely get the disease, unless you die of other causes first.

But in 98 per cent of cases the gene only increases your risk of a condition and that risk may be very small or very uncertain.

Despite the lack of certainty around the impact of many disease-related genes, Dar-Nimrod says there is some evidence that people who test positive for them can become fatalistic and believe they will definitely develop the condition in question.

He says such "genetic determinism" is encouraged by media reports that imply a greater risk from such genes than there actually is.

Unique behavioural experiment

Dar-Nimrod and colleagues set up the first randomized experiment to investigate the psychological and behavioural impact of receiving personalized genetic information of this kind.

"We led people to believe that they either carried a gene related to alcoholism or they didn't," he says.

Alcoholism has been linked to a number of genes as well as environmental factors but there is huge scientific debate over which genes are involved and how important they are, says Dar-Nimrod.

'We didn't give the participants any information that their own $200 couldn't buy them.'— Ilan Dar-Nimrod

In their experiment, carried out at the University of Rochester, in the US, he and colleagues tested 160 undergraduates before and after they were given the bogus genetic test results.

The researchers found people became more emotionally positive when they were told they did not have a gene associated with alcoholism, but became less emotionally positive when they were told they did have gene.

Those who believed they had the gene also felt they had less control over their own drinking, says Dar-Nimrod.

But the study did find that women who believed they had the gene were more likely to sign up for a 'responsible drinking' workshop.

Dar-Nimrod says he and colleagues found that a family history of alcoholism had no effect on the outcomes.

Ethics challenge

Associate professor Jane Halliday of Murdoch Childrens Research Institute describes the study by Dar-Nimrod and colleagues as "quite interesting".

But the sample of people involved would not necessarily be representative of those seeking out genetic tests, says Halliday, who has researched psychosocial impacts of predictive genetic tests.

She also doubts the study would be able to be repeated on the general population because of the ethical issues involved in deceiving the participants.

"Getting ethics approval was a process," says Dar-Nimrod.

But, he says, the research team successfully argued they were only testing scenarios that were already available thanks to direct-to-consumer genetic tests.

"We didn't give the participants any information that their own $200 couldn't buy them," says Dar-Nimrod.

Vexing for policy makers

Some genetic tests involve doctors or genetic counsellors interpreting the significance of the results, but many do not.

Professor Dianne Nicol of the University of Tasmania, who specializes in the legal aspects of genetic testing, says despite the development of regulations covering genetic testing in Australia, people can still get results from direct-to-consumer tests without any expert advice on understanding the results.

"Papers like this really emphasizes the importance of genetic counselling wherever your offering genetic tests," she says.

Nicol says many countries are debating how best to regulate direct-to-consumer tests with France effectively prohibiting them.

"This is an increasingly important issue and it's an issue that's vexing policy makers in Australia and around the world," she says, adding the availability of tests on the internet further complicates the issue.

"It's a borderless environment. So it's going to be quite complicated working out how appropriately to regulate," adds Nicol.