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Background and Aims: The idea that cannabis is a 'gateway drug' to more harmful substances such as opioids is highly controversial, yet has substantially impacted policy, education and how we conceptualize substance use. Given a rise in access to cannabis products and opioid‐related harm, the current study aimed to conduct the first systematic review and meta‐analysis on the likelihood of transitioning from cannabis use to subsequent first‐time opioid use, opioid use disorders (OUD), dependence or abuse. Methods: Following Preferred Reporting Items for Systematic Reviews and Meta‐Analyses (PRISMA) guidelines, pubMed/MEDLINE, Scopus, EMBASE, PsychINFO, Cochrane Central Register of Controlled Trials and Informit Health Collection were searched for full‐text articles assessing the likelihood of transitioning from cannabis to subsequent opioid use, and from opioid use to OUD, abuse or dependence given prior cannabis use. Analysis of subpopulations within studies were discussed narratively, and E‐values were calculated to assess the potential influence of unmeasured confounding. Findings Six studies provided relevant data from the United States, Australia and New Zealand between 1977 and 2017, a total sample of 102 461 participants. Random‐effects analysis of the adjusted pooled effect size indicates that the likelihood of transitioning from cannabis to opioid use, relative to non‐cannabis users, is odds ratio (OR) = 2.76, 95% confidence interval (CI) = 2.26–3.36, whereas the likelihood of transitioning from opioid use to OUD, abuse or dependence given prior cannabis use is OR = 2.52, 95% CI = 1.65–3.84. While the evidence was determined to be of low quality with moderate risk of bias, E‐values suggest that these findings are robust against unmeasured confounding. Conclusion: A systematic review and meta‐analysis found that while people who use cannabis are disproportionately more likely to initiate opioid use and engage in problematic patterns of use than people who do not use cannabis, the low quality of the evidence must be considered when interpreting these findings. [ABSTRACT FROM AUTHOR]

Abstract: Background and aims: Disentangling the putative impact of cannabis on brain morphology from other comorbid substance use is critical. After controlling for the effects of nicotine, alcohol and multi‐substance use, this study aimed to determine whether frequent cannabis use is associated with significantly smaller subcortical grey matter volumes. Design: Exploratory analyses using mixed linear models, one per region of interest (ROI), were performed whereby individual differences in volume (outcome) at seven subcortical ROIs were regressed onto cannabis and comorbid substance use (predictors). Setting: Two large population‐based twin samples from the United States and Australia. Participants: A total of 622 young Australian adults [66% female; μage = 25.9, standard deviation SD) = 3.6] and 474 middle‐aged US males (μage = 56.1SD = 2.6) of predominately Anglo‐Saxon ancestry with complete substance use and imaging data. Subjects with a history of stroke or traumatic brain injury were excluded. Measurements: Magnetic resonance imaging (MRI) and volumetric segmentation methods were used to estimate volume in seven subcortical ROIs: thalamus, caudate nucleus, putamen, pallidum, hippocampus, amygdala and nucleus accumbens. Substance use measurements included maximum nicotine and alcohol use, total life‐time multi‐substance use, maximum cannabis use in the young adults and regular cannabis use in the middle‐aged males. Findings: After correcting for multiple testing (P = 0.007), cannabis use was unrelated to any subcortical ROI. However, maximum nicotine use was associated with significantly smaller thalamus volumes in middle‐aged males. Conclusions: In exploratory analyses based on young adult and middle‐aged samples, normal variation in cannabis use is unrelated statistically to individual differences in brain morphology as measured by subcortical volume. [ABSTRACT FROM AUTHOR]

The article presents several reports regarding addiction of drugs, alcohol and cigarettes. The Australian federal government has stopped its financial support on the Alcohol and Other Drugs Council of Australia (ADCA). The opening of the drug consumption room for drug addicts with infectious disease in Greece which runs by the country's Organization Against Drugs (OKANA). The launch of the plain packaging cigarettes in London, England.