Substance dependence treatable, says neuroscience expert report
Psychosocial, environmental, biological and genetic factors all play significant roles in dependence, says new report published by WHO
18 March 2004 | Geneva/Brasilia - The World Health Organization (WHO) today launched Neuroscience of Psychoactive Substance Use and Dependence, an authoritative report summarizing the latest scientific knowledge on the role of the brain in substance dependence. The report* is the first of its kind produced by WHO, and cites an explosion of advances in neuroscience to conclude that substance dependence is as much a disorder of the brain as any other neurological or psychiatric disorder.
Substance dependence is multifactorial, determined by biological and genetic factors, in which heritable traits can play a strong part, as well as psychosocial, cultural and environmental factors, says the report. It has been known for a long time that the brain contains dozens of different types of receptors and chemical messengers or neurotransmitters. The report summarizes new knowledge on how psychoactive substances are able to mimic the effects of the naturally occurring or endogenous neurotransmitters, and interfere with normal brain functioning by altering the storage, release and removal of neurotransmitters.
The report discusses new developments in neuroscience research with respect to craving, compulsive use, tolerance and the concept of dependence. The report shows that psychoactive substances have different ways of acting on the brain, though they share similarities in the way they affect important regions of the brain involved in motivation and emotions. The report discusses how genes interact with environmental factors to sustain psychoactive substance-using behaviours. This knowledge is the basis of novel diagnostic tools and behavioural and pharmacological treatments.
The report urges increasing awareness of the complex nature of these problems and the biological processes underlying drug dependence. It also supports effective policies, prevention and treatment approaches and the development of interventions that do not stigmatize patients, are community based and cost-effective.
"The health and social problems associated with use of and dependence on tobacco, alcohol and illicit substances require greater attention by the public health community and appropriate policy responses are needed to address these problems in different societies," says WHO Director-General Dr LEE Jong-wook. "Many gaps remain to be filled, but this important report shows that we already know a great deal about the nature of these problems."
United Nations Office on Drugs and Crime (UNODC) data estimates about 205 million people make use of one type of illicit substance or another. The most common is cannabis, followed by amphetamines, cocaine and the opioids. Illicit substance use is more prevalent among males than females, much more so than cigarette smoking and alcohol consumption. Substance use is also more prevalent among young people than in older age groups. UNODC data shows that 2.5% of the total global population and 3.5% of people 15 years and above had used cannabis at least once in one year between 1998 and 2001.
"Substance dependence is a chronic and often relapsing disorder, often co-occurring with other physical and mental conditions," said Dr Catherine Le Galès-Camus, WHO's Assistant-Director General, Noncommunicable Diseases and Mental Health. "While we still do not know to what extent it is curable – given the long-term alterations in brain functioning that result from substance abuse – we do know that recovery from dependence is possible through a number of effective interventions."
The Global Burden of Disease (GBD) from the use of all psychoactive substances, including alcohol and tobacco, is substantial: 8.9% in terms of DALYs (Disability Adjusted Life Years). However, GBD findings re-emphasize that the main global health burden is due to licit rather than illicit substances. Among the 10 leading risk factors in terms of avoidable disease burden cited in The World Health Report 2002, tobacco was fourth and alcohol fifth for 2000, and remains high on the list in the 2010 and 2020 projections. Tobacco and alcohol contributed 4.1% and 4.0%, respectively, to the burden of ill health in 2000, while illicit substances contributed 0.8%. The burdens attributable to tobacco and alcohol are particularly acute among males in the developed countries (mainly Europe and North America). Measures to reduce the harm from tobacco, alcohol and other psychoactive substances are thus an important part of the public health response, says WHO.
"The explosive growth in knowledge in neuroscience in recent decades has contributed new insights into why many people use psychoactive substances even though it causes them harm," says Dr Benedetto Saraceno, Director of WHO's Department of Mental Health and Substance Abuse. "The need for this report comes from these advances, which have shown that psychoactive substances, regardless of their legal status, share similar mechanisms of action in the brain, can be harmful to health and can lead to dependence. The public health impact is enormous and requires a comprehensive approach to policy and programme development."
*The Neuroscience of psychoactive substance use and dependence report is a product of three years work involving the contributions of many experts from around the world. The project began in 2000 with a consultation in New Orleans, USA, during the Congress on Neuroscience. A meeting convened by WHO was attended by representatives of international societies and selected experts in the field. Twenty-five reviews were commissioned, completed and submitted and these formed the basis of the final report. Meetings were held in Geneva and Mexico to discuss the outline of the report and the background papers.
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