The launch of a genetic app titled "How gay are you?" prompted a well-deserved outcry from scientists and the public last month, with media coverage branding it "disgusting" and "the latest bad idea".

The app, which has since been withdrawn from sale, was just one of many available from online app store GenePlaza. Billing itself as "a marketplace for genetic reports", this site offers a wide range of genetic tests that promise to reveal unassailable truths about your sleep, health, neuroses, ancestors, and even your intellect.

The genes tested in each "genetic app" are sourced from scientific reports that have established links between particular genetic variants and particular traits. But the tests are not directly affiliated with the scientists or their studies, and the interpretation and communication of the data produced by the apps is done solely by the developers.

The science behind the test

"How gay are you?" used data from a paper published earlier this year in the prestigious journal Science, showing that sexual orientation has a significant genetic component. According to the research, 8-25 percent of same-sex sexual behaviours can be accounted for by leafing through a few specific pages of the (very) lengthy book that represents your personal genome.

Sexual orientation is complex – thought to be the product of many genes, as well as environmental effects. Although certain gene variants are weakly related to same-sex attraction, the authors of this paper took pains to point out that genetics cannot be used to predict sexual orientation.

So what use is a genetic test if it can't predict individual differences? Not much, most scientists think.

Benjamin Neale, an author on the paper from which the genetic data was derived, sent a letter to GenePlaza asking it to take down the app. A petition to remove the test has attracted around 1,700 signatures.

"How gay are you?" now appears on GenePlaza under the name "122 shades of gray", is no longer available for purchase, and carries a disclaimer stating that it does not predict same-sex attraction and is not associated with the authors of the Science study.

Genetic explanation and sexuality

These tests are not just useless, but potentially dangerous. Information about the genetic basis of traits can have profound effects on the way we understand ourselves and others.

For sexual orientation, the impacts of genetic information seem mixed. One study reported that learning about a biological basis for homosexuality increased anti-gay attitudes, whereas another found the opposite.

Although many people who identify as homosexual endorse a genetically determined view, among sexual minorities this belief seems to be a double-edged sword. Gay men who perceive their sexuality as biological are more certain about their sexual identity, but also view themselves as more different from heterosexuals and in turn experience more self-stigma.

For heterosexual and LGBT populations alike, more research is needed to know what psychological effects the results of genetic tests of this kind might have.

Self-fulfilling prophecy

For some other traits, it is already clear that belief in a genetic basis has a negative effect. Women given biological explanations of gender differences are more likely to hold negative self-stereotypes. In one study, women who were informed that women have genetically inferior mathematical ability went on to perform relatively poorly on a maths test.

This suggests that even if there is no genetic basis for a behaviour or ability, receiving a genetic explanation can become a self-fulfilling prophecy. GenePlaza itself offers a Math Ability app, which promises to tell you how you stack up against the rest of humanity.

Obesity has also been shown to be affected by how we think about genes. Even the most common gene variant associated with obesity only explains a tiny fraction of the variability between individuals. Despite this, a whole cottage industry has sprouted to offer "genetically tailored" diets.

Not surprisingly, GenePlaza offers a My Weight app, with the tagline "can genes determine the size of your jeans?" The answer is possibly yes, albeit via your brain.

Learning that obesity has a genetic basis leads people to discount the importance of exercise and a healthy diet. In one study, participants given information about a link between genes and obesity ate more cookies than those who read a non-genetic explanation.

Perhaps most concerning is GenePlaza's Depression App, which uses data from a 2018 Australian study to provide information about one's genetic risk of depression (although it does feature a disclaimer that its results are "not a diagnosis, a prediction, or a predisposition score").

Social psychologists have shown that when people are told they have a predisposition to depression they are less confident in their ability to cope, and even remember more depressive episodes in their recent past.

Belief in a genetic basis to mental illness not only affects our self-perception, but our attitudes to others too. When thought to be genetically based, people are more negative towards those with a mental illness and more likely to perceive them as dangerous.

These apps are marketed as a curiosity or as harmless fun. But there is danger in claiming to be able to use genetics to predict any aspect of someone's identity, abilities, mental health or sexual orientation. Misunderstanding of genetic information can have grave consequences for those receiving it. The Conversation

Kate Lynch, Postdoctoral Research Fellow, University of Sydney; Ilan Dar-Nimrod, Senior lecturer, University of Sydney, and James Morandini, Postdoctoral fellow, University of Sydney.

This article is republished from The Conversation under a Creative Commons license. Read the original article.