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The relationship between cannabis and psychosis and schizophrenia has tested the field of addiction for decades, and in some ways serves as measure of our ability to provide a credible contribution to public health. As cannabis is used widely, many people are interested in the risks the drug poses to mental health. This paper focuses upon a seminal study examining this, the trajectory of subsequent research findings and what this has meant for understanding and communicating risk factor information. These studies provided evidence of a dose-response relationship between cannabis and psychosis, and that for those individuals with schizophrenia cannabis exacerbated their symptoms. The findings fit with a multi-causal model in which vulnerability interacts with a precipitating agent to produce a disease outcome. Even though this is a common model in epidemiology, it has proved difficult to communicate it in this case. This may be because at a population level the increased risk is weak and the vulnerabilities relatively rare. It may also be because people bring strongly held preconceptions to interpreting a complex multi-causal phenomenon. [ABSTRACT FROM AUTHOR]

Background and aims Prohibitions on producing, distributing and selling cannabis are loosening in various jurisdictions around the world. This paper describes the diversification of cannabis supply laws and discusses the challenges to and opportunities for learning from these changes. Methods We document changes in cannabis supply laws that de jure legalized cannabis production for medical and/or non-medical purposes (excluding industrial hemp) in Australasia, Europe, North America and South America. We also highlight challenges to evaluating these legal changes based on our experiences studying cannabis laws and policies in the United States. Findings As of August 2016, two countries have passed laws to legalize large-scale cannabis production for non-medical purposes at the national (Uruguay) or subnational level (four US states). At least nine other countries legally allow (or will soon allow) cannabis to be supplied for medicinal purposes. Most of the changes in cannabis supply laws have occurred since 2010. The data available in most countries are inadequate for rigorously evaluating the changes in cannabis supply laws. Conclusion The evidence base for assessing changes in cannabis supply laws remains weak. Efforts should focus upon collecting information about quantities consumed and market transactions as well as validating self-report surveys. [ABSTRACT FROM AUTHOR]

Commentary to: Understanding and learning from the diversification of cannabis supply laws [ABSTRACT FROM AUTHOR]

Aims: To quantify changes in (i) potency (concentration of Δ9‐tetrahydrocannabinol; %THC), (ii) price (euros/g of cannabis) and (iii) value (mg THC/euro) of cannabis resin and herbal cannabis in Europe. Design Repeated cross‐sectional study. Setting and participants: Data collected from 28 European Union (EU) member states, Norway and Turkey by the European Monitoring Centre for Drugs and Drug Addiction. Measurements Outcome variables were potency, price and value for cannabis resin and herbal cannabis in Europe, 2006–16. Inflation was estimated using the Harmonised Indices of Consumer Prices. Mixed‐effects linear regression models were used to estimate linear and quadratic time trends, with a random intercept and slope fitted to account for variation across countries. Findings Resin potency increased from a mean [95% confidence interval (CI)] of 8.14% THC (6.89, 9.49) in 2006 to 17.22 (15.23, 19.25) in 2016. Resin price increased from 8.21 euros/g (7.54, 8.97) to 12.27 (10.62, 14.16). Resin increased in value, from 11.00 mg THC per euro (8.60, 13.62) to 16.39 (13.68, 19.05). Quadratic time trends for resin potency and value indicated minimal change from 2006 to 2011, followed by marked increases from 2011 to 2016. Herbal cannabis potency increased from 5.00% THC (3.91, 6.23) to 10.22 (9.01, 11.47). Herbal price increased from 7.36 euros/g (6.22, 8.53) to 12.22 (10.59, 14.03). The value of herbal cannabis did not change from 12.65 mg of THC per euro (10.18, 15.34) to 12.72 (10.73, 14.73). All price trends persisted after adjusting for inflation. Conclusions: European cannabis resin and herbal cannabis increased in potency and price from 2006 to 2016. Cannabis resin (but not herbal cannabis) increased in the quantity of Δ9‐tetrahydrocannabinol per euro spent. Marked increases in resin potency and value from 2011 to 2016 are consistent with the emergence of new resin production techniques in European and neighbouring drug markets. [ABSTRACT FROM AUTHOR]

Abstract: Aims: This review provides an up‐to‐date curated source of information on alcohol, tobacco and illicit drug use and their associated mortality and burden of disease. Limitations in the data are also discussed, including how these can be addressed in the future. Methods: Online data sources were identified through expert review. Data were obtained mainly from the World Health Organization, United Nations Office on Drugs and Crime and Institute for Health Metrics and Evaluation. Results: In 2015, the estimated prevalence among the adult population was 18.4% for heavy episodic alcohol use (in the past 30 days); 15.2% for daily tobacco smoking; and 3.8, 0.77, 0.37 and 0.35% for past‐year cannabis, amphetamine, opioid and cocaine use, respectively. European regions had the highest prevalence of heavy episodic alcohol use and daily tobacco use. The age‐standardized prevalence of alcohol dependence was 843.2 per 100 000 people; for cannabis, opioids, amphetamines and cocaine dependence it was 259.3, 220.4, 86.0 and 52.5 per 100 000 people, respectively. High‐income North America region had among the highest rates of cannabis, opioid and cocaine dependence. Attributable disability‐adjusted life‐years (DALYs) were highest for tobacco smoking (170.9 million DALYs), followed by alcohol (85.0 million) and illicit drugs (27.8 million). Substance‐attributable mortality rates were highest for tobacco smoking (110.7 deaths per 100 000 people), followed by alcohol and illicit drugs (33.0 and 6.9 deaths per 100 000 people, respectively). Attributable age‐standardized mortality rates and DALYs for alcohol and illicit drugs were highest in eastern Europe; attributable age‐standardized tobacco mortality rates and DALYs were highest in Oceania. Conclusions: In 2015 alcohol use and tobacco smoking use between them cost the human population more than a quarter of a billion disability‐adjusted life years, with illicit drugs costing further tens of millions. Europeans suffered proportionately more, but in absolute terms the mortality rate was greatest in low‐ and middle‐income countries with large populations and where the quality of data was more limited. Better standardized and rigorous methods for data collection, collation and reporting are needed to assess more accurately the geographical and temporal trends in substance use and its disease burden. [ABSTRACT FROM AUTHOR]

Aims: To estimate temporal trends in adolescents’ current cigarette, alcohol and cannabis use in Europe by gender and region, test for regional differences and evaluate regional convergence. Design and Setting: Five waves of the European School Survey Project on Alcohol and Other Drugs (ESPAD) from 28 countries between 1999 and 2015. Countries were grouped into five regions [northern (NE), southern (SE), western (WE), eastern Europe (EE) and the Balkans (BK)]. Participants: A total of 223 814 male and 211 712 female 15–16‐year‐old students. Measurements: Daily cigarette use, weekly alcohol use, monthly heavy episodic drinking (HED) and monthly cannabis use. Linear and quadratic trends were tested using multi‐level mixed‐effects logistic regression; regional differences were tested using pairwise Wald tests; mean absolute differences (MD) of predicted prevalence were used for evaluating conversion. Findings: Daily cigarette use among boys in EE showed a declining curvilinear trend, whereas in all other regions a declining linear trend was found. With the exception of BK, trends of weekly drinking decreased curvilinear in both genders in all regions. Among girls, trends in WE, EE and BK differed from trends in NE and SE. Monthly HED showed increasing curvilinear trends in all regions except in NE (both genders), WE and EE (boys each). In both genders, the trend in EE differed from the trend in SE. Trends of cannabis use increased in both genders in SE and BK; differences were found between the curvilinear trends in EE and BK. MD by substance and gender were generally somewhat stable over time. Conclusions: Despite regional differences in prevalence of substance use among European adolescents from 1999 to 2015, trends showed remarkable similarities, with strong decreasing trends in cigarette use and moderate decreasing trends in alcohol use. Trends of cannabis use only increased in southern Europe and the Balkans. Trends across all substance use indicators suggest no regional convergence. [ABSTRACT FROM AUTHOR]

This article presents an editorial in which the authors comment on the legal aspects of cannabis use in Europe. They discuss the inconsistencies associated with punishments related to the use of cannabis as well as other psychoactive substances, citing data from the European Monitoring Centre for Drugs and Drug Addiction.

Commentary to: Considering marijuana legalization carefully: insights for other jurisdictions from analysis for Vermont [ABSTRACT FROM AUTHOR]