Cannabis and driving: A new perspective

Cannabis and driving is an emerging injury‐prevention concern. The incidence of driving while affected by cannabis is rising in parallel with increased cannabis use in the community. Younger drivers are at particular risk. Improvements in research methodology, technology and laboratory testing methods have occurred in the last 10 years. These cast doubt on earlier results and conclusions. Studies now show that cannabis has a significant impairing effect on driving when used alone and that this effect is exaggerated when combined with alcohol. Of particular concern is the presence of cannabis as the sole psychoactive drug in an increasing number of road fatalities and the lack of any structural response to this problem. A review of testing methods, laboratory and real driving studies, and recent epidemiological studies is presented. Suggestions for methods of further data collection and future public policy are made.     

Functional correlates of verbal memory deficits emerging during nicotine withdrawal in abstinent adolescent cannabis users.

BACKGROUND: Cannabis remains the most widely used illicit substance by adolescents and is typically consumed by this population in the context of ongoing tobacco use. Human studies have shown that both cannabis and tobacco exert effects on cognitive function; however, little is known about possible interacting effects of these drugs on brain function and cognition during adolescent development. METHODS: Verbal learning and memory were assessed in 20 adolescent users of tobacco and cannabis and 25 adolescent tobacco users with minimal history of cannabis use. Functional magnetic resonance imaging was used to examine brain function and functional connectivity while a subset of these subjects performed a verbal working memory task. RESULTS: Delayed recall of verbal stimuli deteriorated during nicotine withdrawal among cannabis users but not among comparison subjects. During high verbal working memory load, nicotine withdrawal selectively increased task-related activation of posterior cortical regions and was associated with disruption of frontoparietal connectivity in adolescent cannabis users relative to comparison subjects. CONCLUSIONS: These observations suggest that cannabis use during adolescent development may disrupt neurocircuitry supporting verbal memory formation and that deficits associated with disruption of these neurocircuits are unmasked during nicotine withdrawal.     

Dorsolateral prefrontal cortex N-acetylaspartate/total creatine (NAA/tCr) loss in male recreational cannabis users.

BACKGROUND: Cannabinoids present neurotoxic and neuroprotective properties in in vitro studies, inconsistent alterations in human neuroimaging studies, neuropsychological deficits, and an increased risk for psychotic episodes. METHODS: Proton magnetic resonance spectroscopy ((1)H-MRS), neuropsychological testing, and hair analysis for cannabinoids was performed in 13 male nontreatment-seeking recreational cannabis users and 13 male control subjects. RESULTS: A significantly diminished N-acetylaspartate/total creatine (NAA/tCr) ratio in the dorsolateral prefrontal cortex (DLPFC) was observed in cannabis users (p = .0003). The NAA/tCr in the putamen/globus pallidum region correlated significantly with cannabidiol (R(2) = .66, p = .004). Results of the Wisconsin Card Sorting test, Trail making Test, and D2 test for attention were influenced by cannabinoids. CONCLUSIONS: Chronic recreational cannabis use is associated with an indication of diminished neuronal and axonal integrity in the DLPFC in this study. As chronic cannabis use is a risk factor for psychosis, these results are interesting because diminished NAA/tCr ratios in the DLPFC and neuropsychological deficits were also reported in schizophrenia. The strong positive correlation of NAA/tCr and cannabidiol in the putamen/globus pallidum is in line with neuroprotective properties of cannabidiol, which were also observed in in vitro model studies of Parkinson's disease.     

Implications of the 2018 Canadian Cannabis Act: Should regulation differ for medicinal and non-medicinal cannabis use?⋆

The regulatory framework for access to medical cannabis has been established in Canada since 2001, with the number of patients seeking access growing substantially over the years. With the novel enactment of the Cannabis Act in October 2018, Canada now maintains two distinct mechanisms for accessing cannabis - one for medical cannabis and the other for non-medical cannabis. With two regulatory access mechanisms in place, questions have arisen in the country as to the necessity of maintaining regulatory separation and the integrity of the medical access framework. A single framework would remove the gate-keeping function that the medical profession currently holds, streamlining processes and simplifying the current regulatory landscape. This approach has been advocated for by the Canadian Medical Association, despite objections from multiple stakeholders. Critical questions arise should the medical access framework be dissolved into a single, non medical-based regulatory framework. Insurance coverage, control mechanisms, market incentives, and patient obligations represent some examples of these issues. This paper will expand upon these considerations and highlight why maintaining two separate access mechanismss best serves the Canadian public. As medicinal cannabis continues to be liberated in international jurisdictions, this paper can help to illuminate the current status of medical cannabis in Canada, and provide insights to those from other countries on our current approach and domestic challenges.     

Cannabis laws: an analysis of costs

There is evidence that the use of cannabis is increasing in Australia, with stable black-market prices, despite the 9-year National Campaign Against Drug Abuse, increasing expenditure to enforce the laws against cannabis use, and the seizure of large plantations of cannabis plants. Recent government data are used to estimate the conservative cost of drug-law enforcement against cannabis use as being $329m in 1991-92. Alternatives to the existing regime are examined, including expiation, decriminalization, and legalization.     

The human toxicity of marijuana: a critique of a review by Nahas and Latour

A review entitled “The human toxicity of marijuana” was published in 1992 in the Medical Journal of Australia. The authors claimed that the adverse effects of cannabis use have been trivialized and that the effects are much more serious than earlier reported. We have made a careful study of this review and examined the claims made. We compared the claims of the authors with the information contained in the documents they cited and found that at least 28 of the 35 citations in this article were cited inaccurately. Five of these publications were misquoted, or the findings of the study were not fully reported. Twenty-three citations contained other errors, leaving only six to eight (two citations could not be retrieved because of their obscurity) accurate citations among 35. All of these inaccuracies operate in the direction of finding an adverse effect of marijuana.     

Residual effects of prolonged cannabis administration on exploration and DRL performance in rats

Chronic oral administration of cannabis extract to rats (daily ⁹ dose 20 mg/kg) was examined for its residual effect on open field activity and DRL (differential reinforcement of low-rate responding) performance, following a 2–3-month drug-free period. Locomotor activity during the latter part of an open field test was markedly increased in rats previously treated for either 6 months or 3 months with the drug. The same treatments also produced a significant impairment on a DRL-20 task relative to control subjects' performance. These and other findings (impaired maze learning and facilitated two-way shuttle box avoidance) might mean that cannabis produces long-lasting hippocampal, dysfunction in rats.