NDARC Technical Report No. 143 (2002)
Drug dependence is a serious personal and public health issue in developed countries, such as, Australia, the European Union, the UK, and the USA. It is also becoming a serious problem in developing countries. Many forms of drug dependence are difficult to treat because we lack effective psychosocial or pharmacological treatments.
There is strong research evidence that many addictive phenomena have a neurobiological basis. These include: the fact that psychoactive drugs act on brain neurotransmitters; evidence of a genetic contribution to vulnerability to addiction; the neural mechanisms of tolerance and withdrawal; and the discovery of the neural basis for the rewarding and dependence-producing effects of the major drugs of addiction.
The major potential benefit from an improved understanding of the neuroscience bases of addiction is improved treatment. An improved understanding of the neuroscience basis of addiction requires animal studies of drug effects and drug dependence; experimental studies in humans of drug effects and the neurobiological consequences of drug dependence; clinical trials of new pharmacotherapies for drug dependence; and possibly trials of pharmacological and immunological interventions that aim to prevent addiction.
After a century of debate about the ethics of biomedical animal experimentation, a regulatory compromise has been reached between two sets of competing views. On the one hand, there are those who would abolish all animal experimentation (e.g. proponents of animal liberation and animal rights). On the other, there are those who accept human dominion over animals, according to which animals either have no interests or human interests should always prevail over animals’ when their interests conflict. This regulatory compromise has reduced the amount of animal experimentation that is done by restricting the species on which research can be done; using invertebrates where possible, and minimising animal pain and suffering. Under this compromise, animal research is publicly accepted, including neurobiological addiction research on rats and mice. Proposals to develop primate models of addiction to provide a better model of human addiction may challenge this consensus.
Human experimental studies of the neurobiological basis of addiction raise a number of ethical issues. One is the capacity of addicted persons to give free and informed consent to participate in such studies. So long as participants are not intoxicated or suffering acute withdrawal symptoms at the time they give consent, there is no compelling reason why persons who are drug dependent cannot give free and informed consent. The risks of drug administration, and the use of neuroimaging methods in these experiments, generally do not pose as serious a risk to participants as provocation studies in disorders such as schizophrenia.
The ethical issues raised by clinical trials of new pharmacotherapies have been extensively debated and a consensus has evolved on the conditions that must be met. These include free and informed consent; an acceptable risk-benefit ratio; and protection of participant privacy and confidentiality. Trials with drug dependent persons require special attention to informed consent to ensure that persons are not intoxicated or experiencing withdrawal symptoms when deciding to participate in trials. Placebo comparisons may be ethically acceptable in such trials if there is no effective pharmacotherapy and if participants are also offered good quality psychosocial care.
Preventive pharmacological interventions for addiction do not yet exist and are likely to be highly controversial if they are developed. It is a possibility that looms larger with the development of interventions that have a potential preventive use, foremost among which are drug vaccines. The ethical issues raised by these approaches need to be debated. The risks of stigmatisation and discrimination that are raised by any preventive intervention that identifies high risk subjects will need to be dealt with. So too will issues of consent in minors and the potential risks to participants of immunological interventions.
Neuroscience research on addiction will also affect the long running debate between moral and medical models of addiction by providing a causal explanation of addiction in terms of brain processes. According to one influential version of this approach, addiction is a “brain disease” that results from the flick of a metaphorical switch in the brain produced by chronic drug use. This perspective undermines the moral view that addiction is wholly a matter of individual choice that is best dealt with by punishment and imprisonment.
Medical models of addiction may not be a wholly positive development if they lead to simpleminded social policies. They may, for example, lead to the seductive simplification that if we identify the minority that is genetically and biologically vulnerable to drug dependence, then the rest of the population can use drugs with impunity. They can also lead persons with addiction to abdicate responsibility for their behaviour and to a preoccupation with individual explanations of behaviour, to the neglect of social policies for reducing addiction, including drug control policies. The challenge for the addiction neuroscience community will be to develop an understanding of addiction that gives biology its due without depicting addicts as automatons under the control of receptors in their brains.
The use of pharmacotherapies and drug vaccines under legal coercion is likely to be contentious. It is an arguably ethical policy if the process is under judicial oversight and if offenders are offered constrained choices of (a) whether or not to accept treatment and (b) the type of treatment that they accept. Any coerced use of a cocaine vaccine should be done cautiously and only after considerable clinical experience with its use with voluntary patients. It should be trialed and its safety, effectiveness and cost-effectiveness rigorously evaluated. Such an evaluation also needs to examine any adverse social or ethical consequences.
The most immediate benefit of work on the neuroscience and genetics of addiction may be more effective drugs to assist addicts to stop using their drugs of choice. It may also allow better matching of addicts to treatments. Population screening for multiple genes of small effect that increase susceptibility to drug dependence are unlikely to be practical.
Neuroscience research on addiction is not likely to reduce the need for public health drug control policies. It is much simpler, cheaper and more efficient to discourage the whole population from smoking tobacco, for example, than it is to attempt to make smoking safer by identifying those at highest risk of nicotine addiction or smoking-related disease. The same is arguably true for alcohol and illicit drugs.
The preventive use of a drug vaccine is speculative and ethically contentious. Any trials of their preventive use should be preceded by extensive clinical experience with a vaccine in voluntary patients who are cocaine dependent. A higher standard of safety would be required if it was used preventively and important ethical issues would be raised, such as, consent to its use by minors, the protection of privacy, and the prevention of discrimination.
Citation: Hall, W., Carter,L. and Morley, K.I. (2002) Ethical implications of advances in neuroscience research on the addictions, Sydney: National Drug and Alcohol Research Centre.