Ms Duncan gives an example of one young person interviewed in her research who described her experience of living with the HD risk as harmful for her, and the benefit she experienced when she was tested and discovered that she was not going to develop the illness. Ms Duncan extrapolates from this one example of a good outcome to advocate that predictive testing for adolescents under 18 years of age can have beneficial effects, as not providing testing can be harmful. Ms Duncan does not look realistically at the potential consequences if a young person is found to carry the HD mutation. She assumes this would be no worse than the style of coping that involves a belief that one will develop the illness in the future. Studies have shown that receiving a mutation carrier result does have a more profound psychological impact than such a pre-test belief.
Ms Duncan also asserts that little attention has been given in the literature to, and that we have 'failed to notice', the experience of young people living at risk for a genetic condition. In fact there is substantial literature on the topic of young people and adults living at risk. This dates both from prior to predictive testing being available, and subsequently, focusing on the experiences and decision making of the majority (75 per cent) of adults who have chosen not to undergo such testing since it has been available.
Professionals involved in the counselling and support of families affected by HD and other late-onset genetic disorders are well aware that discovering one's risk for developing such an illness can have a profound effect on a young person, and a variety of coping styles have been documented. With appropriate counselling and support, and developing psychosocial maturity, many young people at risk for HD adjust to living with the uncertainty of being at risk, and are able to get on with their lives and make decisions as young adults without needing to discover their genetic status. Others adopt a form of denial, preferring not to think about their risk, or to face it only if they do develop the illness. Both these approaches offer an explanation for the low uptake of predictive testing worldwide.
Ms Duncan mentions the potential for psychosocial harm associated with predictive testing of young people, and in my experience, this should not be underestimated. Research with adults who have undergone such testing has identified profound long-term psychological effects, particularly for those who learn they will develop the illness, and adverse effects have been reported on aspects of life such as relationships, reproductive decision making and family dynamics.
In addition studies have demonstrated that the areas of the brain involved in judgement and decision making are not fully developed until a person is in their early 20s. Offering a predictive test, with its potentially damaging implications for an at-risk person's future, to a young person whose decision making is restricted by incomplete brain maturation, in my view violates the bioethical principle of 'first, do no harm'. The decision to undergo predictive testing is far more complex than portrayed by the example given by Ms Duncan. It requires psychosocial maturity in areas such as self-identity, anticipation of long-term consequences, and the ability to control impulsive decisions, all of which are gained by ongoing life experience well into adulthood. The international guidelines that set the minimum age for predictive testing for HD as the age of majority were formulated by professionals and family representatives with substantial experience in the effects of HD on individuals and families. Any revision of these guidelines with regard to the appropriate age for testing would need to take into account both the adverse long-term outcomes that have been documented, and the practice wisdom of those providing pre- and post-test counselling in this area.