Clinical Implications of Psychiatric Genetics in the New Millennium
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Jones et al Psychiatric genetics in the new millennium Psychiatric Bulletin 2001), 25,129^131 IAN JONES, LINDSEY KENT, MOLI PAUL AND NICK CRADDOCK opinion Clinical implications of psychiatric genetics in the new &debate millennium -- nightmare or nirvana? We are on the verge of major advances in understanding understanding at different levels of analysis e.g. the pathophysiology of major mental illnesses ^ molecules, neurons, brain regions, neuronal networks, including the likely discovery of several susceptibility psychological mechanisms, family groups, social groups genes for these conditions. For many this holds the and populations) and that understanding at one level is prospect of a future in which improved prevention and likely to inform understanding at other levels. Models of better treatments will end the terror these conditions psychiatric disorders that integrate such diverse findings hold over so many lives Farmer & Owen, 1996; Jones & will be of enormous benefit ^ both academically and, Craddock, 1997,1998). For others the vision is of a `brave more importantly, clinically. new world', our futures mapped from birth by the The fact that mental illness can run in families has genetic hand we have been dealt and in which those with been known for some considerable time but until recently mental illness will suffer increased stigma and discrimina- was of academic interest only. Modern molecular tion Rose, 1998). This debate McGleenan, 1995) occurs genetics provides methods by which susceptibility genes in the dark shadow cast by the eugenic movements of for major psychiatric disorders may be found and it is the 19th and early 20th century Galton, 1943) and the possible that a number of susceptibility genes will be horrors to which they led Hanauske-Abel, 1996; discovered for the major mental illnesses in the early Seidelman, 1996). As we leave the decade of the brain years of this decade ^ a task that will be considerably and enter the new millennium it is an appropriate point to facilitated by the completion of the human genome ask what advances are likely to occur and to consider the project discussed in Craddock & Jones, 1999). Genetics moral and ethical issues that will undoubtedly arise. has proved a powerful tool in the investigation of single gene disorders. The task that remains is to apply the developing methodologies to uncover the pathophy- Challenges facing psychiatry siology of complex disorders such as cardiovascular Despite a revolution in the practice of psychiatry over the disease, diabetes and major psychiatric illness Craddock past 100 years, a number of challenges remain. Diag- & Owen, 1996). Complex disorders result from the inter- nostic uncertainties are common and prognostic predic- action of many susceptibility genes and environmental tion is poor. The number and cost of new drugs increases influences. Rather than rare mutations, the susceptibility year-on-year but treatment response is variable and genes involved are likely to be common variations poly- unpredictable. The debate regarding the optimal environ- morphisms) in the population. Susceptibility genes do not ment for the delivery of services rages on with the act in a deterministic, all-or-nothing manner, but rather balance between hospital, local community and home as a complex interaction of genes and environment that treatment still unresolved. These concerns, although alter the risk of developing a disorder. undoubtedly important in the West, must appear absurd to the majority of people, who have little or no access to mental health services. The appalling stigma still attached Opportunities to mental illness, however, is a reality throughout the world. There are a number of positive implications for the For much of the past century unlike the century discovery of susceptibility genes for mental illness preceding it) psychodynamic causal explanations held reviewed in Craddock et al, 1999). An improved under- sway in psychiatric practice. Over the past 20--30 years standing of aetiological mechanisms is likely to lead to the the biological contribution to much mental illness has development of improved classification systems and been rediscovered and biological approaches to better, more targeted treatments. It is likely to be treatment and research have enjoyed hegemony over possible to predict the response and side-effects of other paradigms. The experiences of illness and its treat- various treatments based on an individual's genotype, so ment, however, always occur in a social context and it is called `pharmacogenetics' Wolf et al, 2000). Preventative vital that this perspective is not forgotten as evidence of strategies are likely to become better informed ^ for biological contributions to illness accrue. There are those example, it may be possible to identify genotypes asso- who adopt a narrow-minded belief system in which only ciated with an increased risk of acute psychotic episodes one particular approach to understanding is deemed being precipitated through the use of illicit drugs. Geno- possible or acceptable. Such extremist positions are ill- type may also predict prognosis and influence decisions informed, naive and extremely detrimental both to regarding the use of prophylactic strategies. Such devel- research and patient care. It is essential to appreciate opments have the potential to become a reality in the that it is possible, and indeed helpful, to seek an relatively near future for Alzheimer's disease, a disorder 129 Jones et al Psychiatric genetics in the new millennium for which several genes have already been identified that considerable workload. Owing to resource implications it influence susceptibility. will be necessary for counselling and testing for common opinion Although the main motivation to search for complex disorders to be provided at the level of primary &debate susceptibility genes for psychiatric disorders is to increase care or the district hospital Kinmonth et al,1998).Are understanding of pathophysiology, and thereby improve these local services willing or able to take on the potential the management of individuals with illness, with the increase in workload? There is also the potential for identification of such genes comes the potential for pre- commercial exploitation of testing for susceptibility genes symptomatic and prenatal testing. Whether this develop- for common disorders Resnik, 1997). With so many ment will occur remains unclear, but theoretically it may families affected by these illnesses, there are vast poten- be possible and therefore the issue of testing needs to be tial profits to be made offering testing over-the-counter considered. For single gene disorders it has usually or even by post. Counselling and testing for genetic proved easier to develop tests than to devise effective disorders also have implications for other family interventions. However, until useful therapeutic options members. Is there a moral duty to inform other family are available it is not clinically useful and may even be members of potential risk, possibly against the wish of unethical to offer testing Parens & Asch, 1999). the initially tested individual, or would this be regarded as However, even at our present level of knowledge there is a breach of confidentiality Wertz & Fletcher, 1991)? It is much evidence to suggest that major psychiatric disor- important to realise that most of these issues are not ders, such as schizophrenia and bipolar disorder, benefit specific to mental illness but apply equally to the large from early recognition and aggressive treatment number of common familial disorders with a genetic Jamison, 1998). Predictive testing for psychiatric illness contribution e.g. heart disease, diabetes, asthma and need not, therefore, lead to therapeutic pessimism, but hypertension). could bring great benefits to those at risk. Certainly Perhaps the most difficult issues raised by these sufferers themselves, when surveyed, show overwhel- advances regard the understanding of our humanity and mingly positive attitudes towards the development of concepts such as free will Kant, 1993) and determinism. tests and a high hypothetical demand if such tests were There is a risk of over-estimating the role of genes, available Smith et al, 1996; Jones et al,1997;Trippitelliet leading to a genetic determinism that denies the moral al, 1998), although, ethically, this should be seen along- accountability of the individual and results in the medica- side the wishes of those who claim the right to genetic lisation of social deviance. Alternatively, the problems of ignorance Takala, 1999). society may be viewed as the consequence of individual genotypes, those in power abrogating responsibility for inequality and misusing science to defend the status quo. Challenges In order to avoid the nihilism that results from genetic determinism, it is important that these misconceptions Few would argue against seeking a better understanding are addressed. of the pathological basis of psychiatric disorders. However, a number of potentially difficult issues are raised by the possibility of testing and need to be Stigma thought through carefully and the issues of pre- symptomatic and prenatal testing are undoubtedly the If presented in a balanced way, an increased under- most problematic. Should the testing of children and standing of the biological contributions to psychiatric young people under 18 years be prohibited Hoffmann & illness is likely to act as a major destigmatising force. Wulfsberg, 1995;