[Show abstract][Hide abstract] ABSTRACT: We systematically reviewed availability and quality of data on the prevalence of use and dependence on meth/amphetamine, cannabis, cocaine and opioids.
Multiple search strategies: (a) peer-reviewed literature searches (1990-2008) using methods recommended by the Meta-analysis of Observational Studies in Epidemiology (MOOSE) group; (b) systematic searches of online databases; (c) Internet searches to find other published evidence of drug use; (d) repeated consultation and feedback from experts around the globe; (e) a viral email sent to lists of researchers in the illicit drug and HIV fields. Data were extracted and graded according to predefined variables reflecting quality of data source.
Qualitative evidence of illicit drug use and dependence was found for most countries, which hold over 98% of the world's population aged 15-64 years. Countries where use was identified but prevalence estimates had not been made (evidence of drug supply, trafficking, reports of use, treatment data) were mainly from Asia, Africa, the Middle East, and Oceania. Estimates of the prevalence of use were located in 77 countries for meth/amphetamine, 95 for cannabis, 86 for cocaine and 89 for opioids. Dependence prevalence estimates existed in very few countries; 9 meth/amphetamine dependence estimates, 7 cannabis dependence estimates, 5 cocaine dependence estimates, and 25 opioid dependence estimates were located.
Data on the extent of meth/amphetamine, cannabis, cocaine and opioid use and dependence must be improved in quality and coverage. Dependence estimates are lacking even in high income countries that have required resources. Responses to illicit drug dependence require better estimates of its scale.
Drug and alcohol dependence 03/2011; 117(2-3):85-101. DOI:10.1016/j.drugalcdep.2010.11.032 · 3.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To conduct a systematic review of mortality among cohort studies of cocaine users.
Three electronic databases were searched (EMBASE, Medline and PsychINFO); other online databases were searched using online libraries and repositories of reports and literature in the drug and alcohol field, with requested contributions from trained librarians and experts. Searches and extraction were undertaken using protocols and cross-checking of decisions by two authors. Additional data were requested from study investigators where studies did not report relevant data.
1911 articles and 2 reports were identified from searches, with data from another four studies located from review articles. Seven cohorts of "problem" or dependent cocaine users reported data that permitted mortality rates to be estimated. Crude mortality rates ranged from 0.53 (95% CI: 0.10-1.58) to 6.16 (95% CI: 5.21-7.11) per 100 PY. Standardised mortality ratios (SMRs) reported in four studies suggested that mortality was four to eight times higher among cocaine users than age and sex peers in the general population.
There are limited data on the extent of elevated mortality among problematic or dependent cocaine users and it is unclear how generalisable the results of these studies may be to other populations of problematic cocaine users. Greater attention to both the method of recruitment, and the characteristics of cocaine users, would enhance our understanding of the mortality risks of problematic cocaine use.
Drug and alcohol dependence 01/2011; 113(2-3):88-95. DOI:10.1016/j.drugalcdep.2010.07.026 · 3.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To review the literature on mortality among dependent or regular users of opioids across regions, according to specific causes, and related to a number of demographic and clinical variables.
Multiple search strategies included searches of Medline, EMBASE and PsycINFO, consistent with the methodology recommended by the Meta-analysis of Observational Studies in Epidemiology (MOOSE) group; grey literature searches; and contact of experts for any additional unpublished data from studies meeting inclusion criteria. Random-effects meta-analyses were conducted for crude mortality rates (CMRs) and standardized mortality ratios (SMRs), with stratified analyses where possible. Meta-regressions examined potentially important sources of heterogeneity across studies.
Fifty-eight prospective studies reported mortality rates from opioid-dependent samples. Very high heterogeneity across studies was observed; pooled all-cause CMR was 2.09 per 100 person-years (PY; 95% CI; 1.93, 2.26), and the pooled SMR was 14.66 (95% CI: 12.82, 16.50). Males had higher CMRs and lower SMRs than females. Out-of-treatment periods had higher mortality risk than in-treatment periods (pooled RR 2.38 (CI: 1.79, 3.17)). Causes of death varied across studies, but overdose was the most common cause. Multivariable regressions found the following predictors of mortality rates: country of origin; the proportion of sample injecting; the extent to which populations were recruited from an entire country (versus subnational); and year of publication.
Mortality among opioid-dependent users varies across countries and populations. Treatment is clearly protective against mortality even in non-randomized observational studies. Study characteristics predict mortality levels; these should be taken into account in future studies.
[Show abstract][Hide abstract] ABSTRACT: To review and summarize existing prospective studies reporting on remission from dependence upon amphetamines, cannabis, cocaine or opioids.
Systematic searches of the peer-reviewed literature were conducted to identify prospective studies reporting on remission from amphetamines, cannabis, cocaine or opioid dependence. Searches were limited to publication between 1990 and 2009. Reference lists of review articles and important studies were searched to identify additional studies. Remission was defined as no longer meeting diagnostic criteria for drug dependence or abstinence from drug use; follow-up periods of at least three years were investigated. The remission rate was estimated for each drug type, allowing pooling across studies with varying follow-up times.
There were few studies examining the course of psychostimulant dependence that met inclusion criteria (one for amphetamines and four for cocaine). There were ten studies of opioid and three for cannabis dependence. Definitions of remission varied and most did not clearly assess remission from dependence. Amphetamine dependence had the highest remission rate (0.4477; 95%CI 0.3991, 0.4945), followed by opioid (0.2235; 95%CI 0.2091, 0.2408) and cocaine dependence (0.1366; 95%CI 0.1244, 0.1498). Conservative estimates of remission rates followed the same pattern with cannabis dependence (0.1734; 95%CI 0.1430, 0.2078) followed by amphetamine (0.1637; 95%CI 0.1475, 0.1797), opioid (0.0917; 95%CI 0.0842, 0.0979) and cocaine dependence (0.0532; 95%CI 0.0502, 0.0597).
The limited prospective evidence suggests that "remission" from dependence may occur relatively frequently but rates may differ across drugs. There is very little research on remission from drug dependence; definitions used are often imprecise and inconsistent across studies and there remains considerable uncertainty about the longitudinal course of dependence upon these most commonly used illicit drugs.
[Show abstract][Hide abstract] ABSTRACT: To examine trends in patterns of cannabis use and related harm in the Australian population between 1993 and 2007.
Analysis of prospectively collected data from: (1) the National Drug Strategy Household Survey (NDSHS) and Australian Secondary Student Alcohol and Drug Survey (ASSADS); (2) the National Hospital Morbidity Database (NHMD); and (3) the Alcohol and Other Drug Treatment Services National Minimum Dataset (AODTS-NMDS).
Australians aged 14 years and over from the general population; students aged 12-17 years; public and private hospital in-patients; public and private in-patients and out-patients attending for drug treatment.
Prevalence of 12-month cannabis use among the general population and secondary students. Proportions in the general population by age group reporting: daily cannabis use; difficulties in controlling cannabis use; and heavy cannabis use on each occasion. Number of hospital and treatment presentations for cannabis-related problems.
Prevalence of past-year cannabis use has declined in the Australian population since the late 1990s. Among those reporting past-year use, daily use is prevalent among 40-49-year-olds, while heavy patterns of use are prevalent among 14-19-year-olds. Hospital presentations for cannabis-related problems reflect similar trends. Past-year cannabis use has decreased among the 10-19-year age group, but those who are daily users in this age group report using large quantities of cannabis.
Despite declines in the prevalence of cannabis use, continued public health campaigns warning of the harms associated with cannabis use are essential, aimed particularly at users who are already experiencing problems. The increasing demand for treatment for cannabis problems in Australia suggests the need for more accessible and more effective interventions for cannabis use disorders.
[Show abstract][Hide abstract] ABSTRACT: • Comparative risk assessments estimate the proportion of a disease that can be attributed to a particular risk exposure and are important guides for health planning. • In observational studies, there has been consistent evidence that cannabis use is associated with an increased risk of schizophrenia and more generally, psychosis. • There is debate about whether such observational evidence is sufficient to infer that cannabis use is a contributory cause of psychosis. • Given the controversy, should the comparative risk assessment in the current revision of the Global Burden of Disease (GBD) include an attribution of psychosis to cannabis use? • We argue that the risk assessment should be included because the evidence is as good as that for many other risk factors included in the GBD, psychotic disorders are associated with substantial unavertable disability, and cannabis use is a potentially preventable exposure.
PLoS Medicine 09/2009; 6(9):e1000133. DOI:10.1371/journal.pmed.1000133 · 14.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Over the past five years, the release of cohort studies assessing the link between cannabis and psychosis has increased attention on this relationship. Existing reviews generally conclude that these cohort studies show cannabis has a causal relationship to psychosis, or at least that one cannot be excluded. Few studies have evaluated the relative strengths and limitations of these methodologically heterogeneous cohort studies, and how their relative merits and weaknesses might influence the way the link between cannabis use and psychosis is interpreted. This paper reviews the methodological strengths and limitations of major cohort studies which have looked at the link between cannabis and psychosis, and considers research findings against criteria for causal inference. Cohort studies that assessed the link between cannabis and psychosis were identified through literature searches using relevant search terms and MEDline, PsycINFO and EMBASE. Reference lists of reviews and key studies were hand searched. Only prospective studies of general population cohorts were included. Findings were synthesised narratively. A total of 10 key studies from seven general population cohorts were identified by the search. Limitations were evident in the measurement of psychosis, consideration of the short-term effects of cannabis intoxication, control of potential confounders and the measurement of drug use during the follow-up period. Pre-existing vulnerability to psychosis emerged as an important factor that influences the link between cannabis use and psychosis. Whilst the criteria for causal association between cannabis and psychosis are supported by the studies reviewed, the contentious issue of whether cannabis use can cause serious psychotic disorders that would not otherwise have occurred cannot be answered from the existing data. Further methodologically robust cohort research is proposed and the implications of how evidence informs policy in the case of uncertainty is discussed.
The International journal on drug policy 09/2009; 21(1):10-9. DOI:10.1016/j.drugpo.2009.09.001 · 2.54 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of the study was to provide empirical data on the severity of hostility among methamphetamine users experiencing psychotic symptoms. Participants were 71 methamphetamine users from the general community who had experienced positive psychotic symptoms in the past year. Psychotic symptoms were defined as a score of 4 or greater on the Brief Psychiatric Rating Scale (BPRS) subscales of suspiciousness, unusual thought content, or hallucinations. The BPRS hostility subscale was used to measure hostility during the most severe symptom episode during the preceding year. Pathological hostility (BPRS score of 4+) was reported by 27% of participants during their most severe episode of psychotic symptoms. Hostility was significantly more common among participants experiencing severe psychotic symptoms (BPRS score 6-7, 42% vs. 15%) or where the psychotic symptoms continued for at least two days (43% vs. 20%). Daily heroin use and low levels of schooling were also correlated with hostility. Clinically significant hostility co-occurs with psychotic symptoms in around one-quarter of methamphetamine users who experience psychosis, and it is more common with severe psychotic symptoms that persist for longer than two days.
American Journal on Addictions 07/2009; 17(3):235-40. DOI:10.1080/10550490802019816 · 1.74 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The market for domestically produced methamphetamine in Australia (sold as ‘speed’ and ‘base’) has been recently supplemented with imported crystalline methamphetamine (‘ice’ or ‘crystal’), the supply of which is thought to involve different organized crime groups than those involved with domestic supply. The existence, or otherwise, of distinct retail markets for these different forms of methamphetamine has important implications for police and public health strategies. The aim of this study was to examine whether there was evidence of distinct retail markets for crystalline methamphetamine and domestically produced forms of the drug. A cross-sectional survey of regular methamphetamine users (n = 309) was undertaken in Sydney, Australia to assess the characteristics of the retail market (consumption, price, perceived purity, availability, purchase location and sale from dealers) for crystalline methamphetamine compared with domestically produced forms of the drug (i.e. speed and base). We did not find any clear evidence of a segregated retail market for crystalline methamphetamine. Only 3% of participants were exclusive crystalline methamphetamine users, and both crystalline methamphetamine and other domestically produced forms of the drug were readily available to consumers, being typically purchased from the same dealers, in the same location and at the same price.
Global Crime 02/2009; 10(1-2-1–2):113-123. DOI:10.1080/17440570902783905
[Show abstract][Hide abstract] ABSTRACT: Increased potency and contamination of cannabis have been linked in the public domain to adverse mental health outcomes. This paper reviews the available international evidence on patterns of cannabis potency and contamination and potential associated harms, and discusses their implications for prevention and harm reduction measures.
A systematic literature search on cannabis potency and contamination was conducted.
Cannabis samples tested in the United States, the Netherlands, United Kingdom and Italy have shown increases in potency over the last 10 years. Some countries have not shown significant increases in potency, while other countries have not monitored potency over time. While there are some grounds to be concerned about potential contaminants in cannabis, there has been no systematic monitoring.
Increased potency has been observed in some countries, but there is enormous variation between samples, meaning that cannabis users may be exposed to greater variation in a single year than over years or decades. Claims made in the public domain about a 20- or 30-fold increase in cannabis potency and about the adverse mental health effects of cannabis contamination are not supported currently by the evidence. Systematic scientific testing of cannabis is needed to monitor current and ongoing trends in cannabis potency, and to determine whether cannabis is contaminated. Additionally, more research is needed to determine whether increased potency and contamination translates to harm for users, who need to be provided with accurate and credible information to prevent and reduce harms associated with cannabis use.
[Show abstract][Hide abstract] ABSTRACT: To examine the extent of physical health impairment among a community sample of methamphetamine users in comparison with the general population, and factors associated with impairment among this group.
A cross-sectional survey of 309 regular methamphetamine users from Sydney. The Physical Component Scale of the Short Form 12 (SF-12) was used to measure impairment in physical health (score < 40). Age-matched general population data for the SF-12 were derived from the Australian National Survey of Mental Health and Well-Being.
Participants had a higher prevalence of impaired physical health compared to the Australian general population (20% vs. 10%, p<0.05), but this effect occurred among only dependent methamphetamine users over 24 years of age (25 - 34 years, 23% vs. 10%; 35 - 44 years, 41% vs. 12%). Methamphetamine dependence remained significantly predictive of impaired physical health after adjusting for age and other confounding factors. Opioid pharmacotherapy was also related strongly to poor physical health, accounting for 63% of participants with physical impairment. Other factors associated with impaired physical health were being female, having less than 10 years of schooling, and having been diagnosed previously with an anxiety disorder (p<0.05).
Methamphetamine users are more likely to report impaired physical health than the general population, but this impairment is specific to older methamphetamine users who are dependent on the drug, particularly those who are enrolled in opioid pharmacotherapy.
Drug and Alcohol Review 04/2008; 27(5):482-9. DOI:10.1080/09595230801914776 · 1.55 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The aim of the current study was to determine whether crystalline methamphetamine users are more dependent on methamphetamine than people who use other forms of the drug, and if so, whether this could be accounted for by their methamphetamine use history.
A structured face-to-face interview was used to assess drug use patterns and demographics among a convenience sample of 309 regular methamphetamine users from Sydney, Australia. Dependence on methamphetamine in the past year was measured using the Severity of Dependence Scale. The use of crystalline methamphetamine in the past year was confirmed using a photographic identification sheet.
Participants who had used crystalline methamphetamine in the past year were significantly more likely to be dependent on methamphetamine than participants who took only other forms of methamphetamine during this time (61% versus 39%). Methamphetamine dependence was also associated with injecting or smoking methamphetamine (67% and 58%, respectively versus 30% for intranasal or oral use), using methamphetamine more than weekly (68% versus 34%), having used the drug for more than 5 years (61% versus 36%), and having used 'base' methamphetamine in the past year (59% versus 39%). Crystalline methamphetamine use remained significantly associated with methamphetamine dependence after adjusting for these patterns of methamphetamine use.
Methamphetamine users who took crystalline methamphetamine in the past year were more likely to be dependent than methamphetamine users who had not taken the crystalline form of the drug during this time.
Drug and Alcohol Dependence 01/2007; 85(3):198-204. DOI:10.1016/j.drugalcdep.2006.04.007 · 3.42 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To examine the prevalence of psychotic symptoms among regular methamphetamine users.
Participants were recruited from Sydney, Australia, through advertisements in free-press magazines, flyers and through word-of-mouth.
Methamphetamine users (n = 309) who were aged 16 years or over and took the drug at least monthly during the past year.
A structured face-to-face interview was used to assess drug use, demographics and symptoms of psychosis in the past year. Measures of psychosis included: (a) a psychosis screening instrument derived from the Composite International Diagnostic Interview; and (b) the Brief Psychiatric Rating Scale subscales of suspiciousness, unusual thought content, and hallucinations. Dependence on methamphetamine was measured using the Severity of Dependence Scale.
Thirteen per cent of participants screened positive for psychosis, and 23% had experienced a clinically significant symptom of suspiciousness, unusual thought content or hallucinations in the past year. Dependent methamphetamine users were three times more likely to have experienced psychotic symptoms than their non-dependent counterparts, even after adjusting for history of schizophrenia and other psychotic disorders.
The prevalence of psychosis among the current sample of methamphetamine users was 11 times higher than among the general population in Australia. Dependent methamphetamine users are a particularly high-risk group for psychosis.
[Show abstract][Hide abstract] ABSTRACT: n this issue, Louisa Degenhardt and Wayne Hall provide an insightful and accessible overview of the literature on the relation between cannabis use and psychosis. They also present some of the policy implications of this relation. The first paper reviews the evidence for a causal relation between cannabis use during adolescence and early adulthood and subsequent diagnosis of a psychotic disorder or experience of psychotic symptoms (1). The authors present research that has established an association between cannabis use and psychosis that cannot be explained by chance. They then focus on recent longitudinal studies that have investigated the causal direction of the association and that have attempted to rule out other explanations for the association by controlling for potential confounders, such as other drug use and personal characteristics. Degenhardt and Hall con- clude that these studies suggest that among vulnerable indi- viduals cannabis use does predict an increased risk of experiencing psychotic symptoms or of developing a psy- chotic disorder. Self-medication is rejected as a likely expla- nation for the relation. Given the evidence of the involvement of the cannabinoid system in psychosis, Degenhardt and Hall also argue that the causal relation between cannabis and psychosis is biologically plausible. The second paper places this evidence in a broader context by comparing it with the evidence for the health effects of other drug use (2). In light of the evidence presented, the authors discuss the implications for public policy. They conclude that young people with mental health problems should be discour- aged from using cannabis and that all young people should be informed of the mental health risks of cannabis use. Hall and Degenhardt examine the controversial topic of how evidence for harms, in this case the risk of developing psychosis as a result of cannabis use, should affect the laws and penalties associated with cannabis. The authors argue that, while we should ensure that legislation and penalties do not make it eas- ier for young people to begin using cannabis, there are many other issues, such as the social harm associated with personal cannabis use being a criminal offence, to consider with respect to cannabis laws and penalties. It is clear from the research literature that, if an individual is prone to serious psychotic illness, the use of cannabis may trigger an episode. The extent of the problem in terms of psy- chiatric cases must be clarified and put into perspective. Internationally, cannabis use is increasingly prevalent, and it now attracts a great amount of attention from the public, from families of users, from concerned policy-makers, and from mental health clinicians who are increasingly aware of cannabis use among their patients. One of the consequences of focusing on cannabis and psychosis is that other harms associated with cannabis use are overshadowed. The lack of recognition of the mental health effects associated with other drug use (such as alcohol, cocaine, opioids, and amphet- amines) is another consequence. Hall and Degenhardt clearly point to the much larger problem of amphetamine psychosis presentations, despite the comparatively fewer users of amphetamine (2). Degenhardt and Hall discuss important cannabis-related harms that include the prevalence of cannabis dependence in the community, the social harms associated with cannabis use, cognitive dysfunction, educational and vocational failure, and the large amount of money spent on cannabis by its regular users. A myopic view will focus on cannabis' relation to psy- chosis and will miss the larger picture of the effects of canna- bis on general health and well-being. The recent development of an Australian National Cannabis Strategy (3) demonstrates the need for public education on the harms associated with cannabis use; however, the public and professional communities need a broader understanding, from credible sources, of the range of harms that cannabis use brings and not a single focus on psychosis symptoms and disorders. When read carefully, Degenhardt and Hall's contributions can create an understanding of the strength of evidence and provide some credible ways to deal with the continued growth of cannabis use in many Western countries. Their call for the introduction of these policy options is an important signpost in the process of better dealing with cannabis problems.
Canadian journal of psychiatry. Revue canadienne de psychiatrie 09/2006; 51(9):554-5. · 2.55 Impact Factor