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Theresa M Marteau a Psychology and
Genetics Research Group, GKT Medical School, King's College London,
Thomas Guy House, London SE1 9RT, b Cancer Control and
Population Science, Georgetown University Medical Center, 2233 Wisconsin Avenue, Washington, DC 20007-4101, USA
Correspondence
to: T M Marteau theresa.marteau{at}kcl.ac.uk
Predictive genetic testing is currently used mainly for
untreatable conditions, such as Huntington's disease, or prenatal detection of serious genetic disorders such as cystic
fibrosis. Prenatal tests are usually accompanied by an offer
of termination of affected pregnancies. Genes have now been isolated
that are associated with potentially preventable diseases such as heart disease and cancer and with increased risk from smoking and obesity. This has raised the possibility of providing predictive information to many more people. Such information may eventually reduce disease by
facilitating the development of better targeted and more effective treatment.
Informing people of their genetic susceptibility to disease may
motivate them to change their behaviour to reduce their risks. However,
changing behaviour is often difficult. In this article we review the
limited evidence concerning behavioural responses to genetic
information on risk. We use this and the literature on behavioural
change to consider if and how behaviour might be changed in response to
genetic information.
We searched Medline, PsycINFO, and the Social Science
Citation Index using the following terms: health behavior; illness
behavior; genetic screening or mass screening; cancer screening, health screening, mammography, or preventive medicine; genetic counselling, genetic disorders, genetic linkage, or genetics; and at risk
populations. In addition, we searched citations of key papers, recent
reviews of the subject, and conference proceedings (using the Web of Science).
Just telling people that they are at risk of developing a
disease is rarely sufficient to change behaviour.1 The
interventions that are most likely to work are those that are based on
theories of behavioural change.
2 3
These theories suggest
that motivation to change a health related behaviour is influenced by
two sets of beliefs: firstly, beliefs about current behaviour (is it
putting me at risk? will changing it reduce my risk?) and, secondly,
beliefs about the ability to change behaviour (how easy will it be for me to change my behaviour? do I have the skills to adopt this new
behaviour?).
4 5
Most studies use intention to change behaviour as the measure of motivation.
Although intention to change is associated with an increased likelihood
of doing so, it predicts only about 30% of the variance in behavioural
change. There are many reasons for this, but particularly important is
the likelihood that people with good intentions fail to act on
them.
6 7
Few interventions to induce change have been
proved effective, and even these succeed in changing behaviour in only
a minority. Interventions with evidence of effectiveness are available
for smoking, physical activity, and attendance at screening
programmes.
2 8
Providing people with personalised information on risk is not
new.9 The question is whether responses will be any
different if the information is based on DNA.
Responses to any information on risk are shaped by pre-existing
perceptions and by the way the information is
presented.
1 10
Genetic risk information could both
increase and decrease motivation to change behaviour. It might increase
motivation by strengthening the belief that current behaviour, combined
with a genetic predisposition, is putting a person at increased risk of
disease. It could also increase motivation by strengthening belief in
the effectiveness of a treatment recommended on the basis of genotypic
information. Alternatively, given a common perception that genetic
risks are immutable, it might decrease motivation by weakening beliefs
that changing behaviour will reduce risks.
11 12
Genetic
risk information may also weaken belief in the ability to change
behaviour Inherited cancer
Summary points
Changing behaviour is difficult
Behavioural change is most likely in motivated people who participate
in effective interventions
Providing people with genetic information on risk may not increase
their motivation to change behaviour and in some cases may decrease
motivation
Behavioural change may be more likely if people are persuaded that
changing their behaviour can reduce the risk of an adverse health
outcome and they are given access to evidence based interventions
Further research is needed to evaluate programmes in which genetic risk
information is given, including evaluation of different ways of giving
information
Effective interventions to change behaviour after provision of
information on risk need to be developed
![]()
Methods
![]()
Changing health related behaviour
![]()
Changing behaviour in response to genetic risk
for example, among people who learn that they have a genetic
vulnerability to nicotine addiction. We consider the evidence for these
hypotheses in relation to three important health problems: cancer,
heart disease, and smoking.
Isolation of genes for susceptibility to cancer has made it
possible to provide predictive genetic testing for risk of breast
cancer, hereditary non-polyposis colon cancer, familial adenomatous
polyposis, and prostate cancer.13-15 These advances
enable appropriate detection and risk management strategies to be
implemented years before cancer develops, with the potential to reduce
mortality.
16 17
However, in order for such testing to
reduce risk and mortality, people who are at risk must change their
behaviour.
Heart disease
People who have or perceive a family history of heart disease are
not more or less likely than other people to engage in behaviours
that reduce the risk of heart disease, such as not smoking or being
physically active.
24 25
Perceiving a family history of
heart disease was associated with a sense of fatalism in less than 15%
of participants in a population based survey of over 2000 adults.26 It remains to be seen whether people who have
genetic testing to ascertain their risk of heart disease will have
similar low rates of fatalism.
Smoking
Gene variants that modify the adverse effects of health behaviours
are much more common than susceptibility genes such as those that
confer hereditary cancer and heart disease. An important example of
gene-behaviour interaction is the genes that increase susceptibility to
the adverse health effects of smoking.
29 30
Only one
study has examined the effect of testing for common gene variants
on smoking behaviour.
31 32
This randomised controlled
trial compared the smoking beliefs and behaviours of smokers who
received smoking counselling plus genetic test results indicating a
twofold to threefold increased risk of smoking related lung cancer with
those of smokers who received counselling only. Smokers who had genetic
testing showed positive changes in perceptions of risk and beliefs
about quitting. However, although they made more attempts to quit, they
were no more likely to stop smoking. These preliminary results suggest
that genetic information may not lead to behavioural changes, even when
there is an unequivocal risk reduction strategy available.
| |
How might behavioural change be promoted? |
|---|
The current evidence suggests that providing people with DNA derived information about risks to their health does not increase motivation to change behaviour beyond that achieved with non-genetic information. For some people, genetic information may even reduce motivation to change behaviour. Genetic information could facilitate behavioural change if people are offered effective risk reducing interventions that are tailored to their DNA based risk, as could be the case for smoking. This, however, is likely to be the exception for the foreseeable future.
|
Educational resources
Kjourny MJ, Burke W, Thompson EJ, eds. Genetics and public health in the 21st century: using genetic information to improve health and prevent disease. New York: Oxford University Press, 2000 BMJ archive Marteau TM et al. Psychological responses to genetic testing. BMJ 1998:316:693-6. http://bmj.com/cgi/content/full/316/7132/693 Levitt M. The ethics and impact on behaviour of knowledge about one's own genome. BMJ 1999;319:1283. http://bmj.com/cgi/content/full/319/7220/1283 |
People's motivation to change behaviour may be increased by strengthening two sets of beliefs: firstly their beliefs that changing behaviour can reduce risks and, secondly, their beliefs in their ability to change. The first set of beliefs might be altered by using bar charts to show health risks before and after behavioural change, similar to those used in programmes to manage cardiovascular risk.40 Beliefs about ability to change might be altered by cognitively based interventions of the type used in cognitive behaviour therapy. 40 41 The effectiveness of these methods in increasing motivation to change behaviour in the context of genetic testing requires empirical investigation. As with all information on risk, behaviour is more likely to be changed if the information is presented as part of an intervention that is known to be effective in changing behaviour
It will also be important to ensure that people who are found not to be at increased risk do not develop a false sense of reassurance, feeling invulnerable to the adverse effects of their risky behaviour. Such people need to understand that they have a residual (albeit lower) risk of developing the condition and be encouraged to engage in risk reducing behaviours relevant for the general population.
The human genome project shows what can be achieved with sufficient resources and concerted international effort. Perhaps what is needed now is a human behavioural change project to ensure that applications from the human genome project are realised in practice.
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Footnotes |
|---|
TMM is funded by The Wellcome Trust and CL is funded by the National Cancer Institute and the National Human Genome Research Institute.
Competing interests: None declared.
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