DNA testing has 'no impact on lifestyle choices'

A recent study has suggested that genetic tests to assess the risk of diseases like diabetes and lung cancer do little to motivate people to change their behaviour.

The research, led by the University of Cambridge and published last week in the British Medical Journal, challenged the view that better informed people are willing or able to make lifestyle adjustments.

Researchers analysed 18 published medical studies that assessed the impact of DNA testing for Alzheimer's and Crohn's disease, as well as diabetes, heart disease, obesity and various forms of cancer, on over 6000 participants.

They conclude that the available evidence suggests that communicating risk estimates has 'little or no effect' on health behaviour, commenting: 'Existing evidence does not support expectations that such interventions could play a major role in motivating behaviour change to improve population health.'

Professor Theresa Marteau, Director of the Behaviour and Health Research Unit at Cambridge University and lead investigator of the study, explained: 'Expectations have been high that giving people information about their genetic risk will empower them to change their behaviour – to eat more healthily or to stop smoking, for example – but we have found no evidence that this is the case.'

Genetic testing allows people to assess whether they have a risk of developing certain illnesses. The technique has become more prevalent in recent years, and popularised by celebrities like Angelina Jolie. Some products – such as those provided by 23andMe – are marketed directly to patients. However, the use of genetic testing has proved controversial. Just because a patient carries a particular gene, it does not mean that they will develop the condition associated with it.  

The authors of the BMJ study recognise that genetic testing may be beneficial if used in tandem with other diagnostic tools. One of the study's co-authors, Dr Gareth Hollands, explained: 'DNA testing, alone or in combination with other assessments of disease risk, may help clinicians identify individuals at greatest risk and allow them to target interventions such as screening tests, surgery, and drug treatments.'

The BMJ study also underlines the value of screening large populations, as it may help identify which groups are at risk of which diseases, and for other behavioral interventions to be targeted appropriately.

But, given the expectations now placed on genetic testing in public health, the BMJ study calls for further research to assess the efficacy of genetic testing in altering behaviour. It notes that the language through which the genetic risk is explained may be important in effecting behaviour, but that more research is required.

Professor Marteau also noted that while there is no evidence to support the view that genetic testing motivates people to change their behaviour, there is no evidence to suggest that it might demotivate or discourage them either.