The global epidemiology and burden of psychostimulant dependence: Findings from the Global Burden of Disease Study 2010☆
Introduction
Cocaine and amphetamines are the two major psychostimulants used for recreational purposes globally. In 2012, it was estimated that there were 34 million amphetamine users worldwide (range 14–53 million) and 17 million cocaine users (range 14–21; The United Nations Office on Drugs and Crime (UNODC), 2013). The UNODC (2012) has estimated that amphetamines were the second most commonly used illicit drug type worldwide, after cannabis. Amphetamine users outnumbered opioid users in all regions except Europe and South Asia. Cocaine was less commonly used globally, but was the second most commonly used illicit drug in Southern Africa, North America, South America, the Caribbean and West and Central Europe (UNODC, 2009).
Cocaine is produced from the Erthroxylon coca plant, which is native to the Andes Mountains in South America. It is a central nervous system (CNS) stimulant that has a short half-life. It increases levels of dopamine, serotonin and norepinephrine in synapses in brain areas implicated in reward by blocking the reuptake of these monoamines (Kuhar et al., 1991, World Health Organization, 2004). Cocaine comes in many forms (paste, cocaine hydrochloride (HCL), crack cocaine, paco, basuco) but cocaine HCL and crack are the most commonly used forms (WHO/United Nations lnterregional Crime and Justice Research Institute, 1995) They may be snorted, injected and smoked (American Psychiatric Association, 1994, WHO/United Nations lnterregional Crime and Justice Research Institute, 1995, UNODC, 2009).
Many people use cocaine occasionally, but a minority develop a pattern of heavy and frequent use that produces cocaine dependence (WHO/United Nations lnterregional Crime and Justice Research Institute, 1995). According to the American Psychiatric Association's Diagnostic Statistical Manual (DSM), a cocaine dependent person develops a tolerance to cocaine and reduces their social, recreational and occupational activities as a result of their drug use (American Psychiatric Association, 1994). A withdrawal syndrome has been identified that includes physiological symptoms such as agitation, fatigue, increased appetite and unpleasant or vivid dreams, disturbances in functioning and psychological distress with an onset a few hours to a few days after last use (American Psychiatric Association, 1994).
Amphetamines are central nervous system (CNS) stimulants that were first synthesised more than a century ago for medical use. Multiple forms of amphetamines exist, including diverted pharmaceutical amphetamines. Methamphetamine and amphetamine are thought to be the most commonly used types (UNODC, 2007, UNODC, 2009). They can come in pill, powder or crystalline forms that vary in purity. They can be taken via different routes: pills are most typically swallowed, powder is often taken intranasally or via injection, whereas the crystalline form can be smoked, injected, or heated and its vapours inhaled. There is a meth/amphetamine dependence syndrome (Topp and Darke, 1997, Topp and Mattick, 1997a, Topp and Mattick, 1997b) that is increasingly recognised by international and national organisations as a significant public health and public order issue (UNODC, 2008a, UNODC, 2008b, UNODC, 2009).
Both cocaine and amphetamine dependence have been associated with negative social, physical and psychological outcomes (Degenhardt and Hall, 2012). These include psychotic symptoms, cardiovascular disease, blood borne viral infections HIV, hepatitis C (HCV) and hepatitis B (HBV), and sexually transmitted infections (Cregler, 1989, Satel et al., 1991, Marzuk et al., 1992, Cornish and O’Brien, 1996, Roy, 2001, Falck et al., 2003, Darke and Kaye, 2004, Kaye and Darke, 2004, Degenhardt et al., 2005, Haasen et al., 2005, Mooney et al., 2006, Ribeiro et al., 2006, Conner et al., 2008, Mathers et al., 2008, Degenhardt and Hall, 2012).
There has never been a systematic review and estimate of global, regional and country-level patterns of amphetamine and cocaine dependence and associated health burden. Such information is crucial to inform policy and programming efforts to prevent and treat these disorders.
The global burden of disease (GBD) framework was initiated by the World Bank for its 1993 World Development Report (World Bank, 1993) and uses information on mortality and disability caused by a given disease or injury to estimate the years of life lost due to premature mortality (YLLs) and the years of life lived with disability (YLDs). YLLs and YLDs can be summed to give disability-adjusted life years (DALYs), an overall measure of disease burden. Previous GBD studies have not estimated the burden of disease due to cocaine and amphetamine dependence (Murray and Lopez, 1996, Prince et al., 2007, WHO, 2008).
GBD 2010 refined the methods used to estimate disease burden. It estimated the burden of 291 diseases and 67 risk factors, by age, sex, 187 countries, and 21 world regions, for 1990 and 2010 (Lim et al., 2012, Lozano et al., 2012, Murray et al., 2012, Salomon et al., 2012, Vos et al., 2012). GBD 2010 conducted systematic reviews of the literature to capture all the available epidemiological data, from 1980 onwards, on the prevalence, incidence, remission and mortality from psychostimulant dependence. Other methodological improvements included using a Bayesian meta-regression approach to model epidemiological data. Among other things, this approach carried forward the effects of uncertainty in epidemiological parameters into the final burden estimates. Disability was quantified for a more comprehensive list of health states than in 2000, using more representative survey data. Burden estimates were also adjusted for the effects of comorbidity (Murray et al., 2012, Vos et al., 2012).
This study uses the systematic reviews of the epidemiology of cocaine and amphetamine dependence (Singleton et al., 2009, Calabria et al., 2010, Degenhardt et al., 2011a, Degenhardt et al., 2011b). In this study, we: (1) assemble these data into comprehensive disease models of cocaine and amphetamine dependence; (2) generate global and regional estimates of the prevalence of these forms of dependence; and (3) present global and regional estimates of YLDs, YLLs and DALYs attributable to cocaine and amphetamine dependence.
It is important to note that this paper focuses exclusively upon the direct burden of these disorders. It does not detail the attributable burden of other health outcomes for which cocaine and amphetamine dependence are risk factors. In GBD 2010, the only outcome of these disorders that met the criteria for being included in the comparative risk assessment component (Lim et al., 2012) was suicide (Degenhardt et al., 2013, Degenhardt et al., 2014b). The attributable burden of amphetamine and cocaine dependence as risk factors for suicide has been detailed elsewhere (Ferrari et al., 2014). Although HIV, HBV and HCV are associated with cocaine and amphetamine dependence, we examined burden of injecting drug use overall due to these viruses, rather than specific types of injecting drug use (Degenhardt et al., 2013).
We did not explicitly estimate the prevalence and disease burden related to MDMA (ecstasy) dependence. Debate continues about a potential dependence syndrome (Degenhardt et al., 2010a); there was also no MDMA dependence syndrome included in the American Psychiatric Association's Diagnostic and Statistical Manual (DSM) or by the WHO in the International Classification of Diseases (ICD).
Section snippets
Case definition
The case definition of cocaine dependence included cases meeting the Diagnostic and Statistical Manual of Mental Disorders (DSM; American Psychiatric Association, 2000) or International Classification of Diseases (ICD; WHO, 1993) diagnostic criteria for cocaine dependence (DSM:304.20; ICD:F14.2). Amphetamine dependence included cases meeting the DSM (American Psychiatric Association, 2000) or ICD (WHO, 1993) diagnostic criteria for amphetamine dependence (DSM:304.40; ICD:F15.2).
Epidemiological data and prevalence modelling
We drew on data
Epidemiological models
There was empirical evidence of cocaine use and dependence found for 182 countries (Degenhardt et al., 2011a). These countries covered 98% of the world's population aged 15–64 years. More than one half of these countries (n = 96) reported evidence of cocaine use in the absence of data on the extent of its use. Of the 86 countries that reported prevalence of use, only 5 had estimated the prevalence of cocaine dependence.
There was evidence of meth/amphetamine use or dependence in 181 countries of
Discussion
This study summarised the estimated epidemiology of cocaine and amphetamine dependence globally, and the burden of disease these disorders are thought to cause. Our findings highlight the scale and impact of cocaine and amphetamine dependence as public health problems. Psychostimulant disorders are the most common illicit drug use disorders after opioids (Degenhardt et al., 2013). Similar to other substance use and mental disorders they have a substantial impact because of their onset in
Role of funding source
Louisa Degenhardt is supported by an Australian National Health and Medical Research Council (NHMRC) Principal Research Fellowship #1041742. Wayne Hall is funded by an NHMRC Australia Fellowship. The National Drug and Alcohol Research Centre at the University of NSW is supported by funding from the Australian Government under the Substance Misuse Prevention and Service Improvements Grants Fund. Amanda Baxter and Harvey Whiteford are affiliated with the Queensland Centre for Mental Health
Contributors
LD, HAW, AJB, and YYL worked with the members of the GBD core group, namely TV, and AF, to undertake the systematic reviews, the epidemiological modelling and prepare the burden estimates. NJ analysed mortality data. LD prepared the first draft of the paper with assistance from AJB, YYL and WH; all other authors contributed to subsequent drafts. All authors contributed to and approved the final manuscript.
Conflict of interest
None to declare.
Acknowledgements
The GBD Mental Disorders and Illicit Drug Use Expert Group which comprised: Harvey Whiteford (Co-Chair), Louisa Degenhardt (Co-Chair), Oye Gureje, Wayne Hall, Cille Kennedy, Ron Kessler, John McGrath, Maria Medina-Mora, Guilherme Polanczyk, Martin Prince, and Shekhar Saxena. Thanks to staff who contributed to aspects of the systematic reviews: Anna Roberts and Mary Kumvaj; and to Roman Scheurer for his assistance in creating some of the maps.
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Supplementary material can be found by accessing the online version of this paper. Please see Appendix A for more information.