Ischaemic strokes with reversible vasoconstriction and without thunderclap headache: a variant of the reversible cerebral vasoconstriction syndrome?

Headache Attributed to Reversible Cerebral Vasoconstriction Syndrome (RCVS)

Reversible cerebral vasoconstriction syndrome (RCVS) is a condition with variable outcomes presenting a new onset thunderclap headache accompanied by focal neurological symptoms or seizures. It can be idiopathic or arise secondarily to a variety of trigger factors. The condition is increasingly recognized in clinical practice, but many facets remain poorly understood. This article aims to clarify the headache characteristics in RCVS, the temporal association of angiographic findings, the potential association of the condition with SARS-CoV-2 infection, and the clinical presentation of RCVS in children and is based on a systematic PRISMA search for published analytical or large descriptive observational studies. Data from 60 studies that fulfilled specific criteria were reviewed. Most people with RCVS exhibit a typical thunderclap, explosive, or pulsatile/throbbing headache, or a similar acute and severe headache that takes longer than 1 min to peak. Atypical presentations or absence of headaches are also reported and may be an underrecognized phenotype. In many cases, headaches may persist after resolution of RCVS. Focal deficits or seizures are attributed to associated complications including transient ischemic attacks, posterior reversible encephalopathy syndrome, ischemic stroke, cerebral edema, and intracranial hemorrhage. The peak of vasoconstriction occurs usually within two weeks after clinical onset, possibly following a pattern of centripetal propagation, and tends to resolve completely within 3 months, well after symptoms have subsided. There are a few reports of RCVS occurring in relation to SARS-CoV-2 infection, but potential underlying pathophysiologic mechanisms and etiological associations have not been confirmed. RCVS occurs in children most often in the context of an underlying disease. Overall, the available data in the literature are scattered, and large-scale prospective studies and international collaborations are needed to further characterize the clinical presentation of RCVS.

RCVS: by clinicians for clinicians-a narrative review

BACKGROUND/OBJECTIVE

Reversible cerebral vasoconstriction syndrome may be underdiagnosed. It can be accompanied by various complications, mainly intracerebral hemorrhage and ischemic stroke. The clinical presentation of this condition varies according to its localization. The aims of this review are to raise awareness of the disease, especially in the presence of corresponding risk factors; to connect its precipitating factors, pathophysiology, and complications; and to compare various differential diagnoses of vasoconstriction.

METHODS

A review of the literature in PubMed/MEDLINE and Google Scholar was conducted from May 1997 until May 2022.

RESULTS

Reversible cerebral vasoconstriction syndrome, which is a clinical-radiological syndrome, is mainly characterized by the occurrence of thunderclap headache and widespread vasoconstriction. The most common precipitating factors are the use of vasoactive substances and postpartum status. The pathophysiology is currently assumed to include two mechanisms: sympathetic overactivity and endothelial dysfunction. From these mechanisms, it is possible to derive potential complications as well as the most important differential diagnoses: posterior reversible encephalopathy syndrome, convexity subarachnoid hemorrhage, ischemic and hemorrhagic stroke, and primary angiitis of the central nervous system.

CONCLUSION

In general, the outcome of reversible cerebral vasoconstriction syndrome is very good. Vasospasm as well as thunderclap headache attacks can be fully reversible, and > 90% of patients are functionally independent at discharge.

Secondary Headache Disorders: Approach, Workup, and Special Considerations for Select Populations

Headache is one of the most common diagnoses in neurology. A thorough understanding of the clinical presentation of secondary headache, which can be life-threatening, is critical. This review provides an overview of the diagnostic approach to a patient with headache, including discussion of "red," "orange," and "green" flags. We emphasize particular scenarios to help tailor the clinical workup to individual circumstances such as in pregnant women, when particular attention must be paid to the effects of blood pressure and hypercoagulability, as well as in older adults, where there is a need for higher suspicion for an intracranial mass lesion or giant cell arteritis. Patients with risk factors for headache secondary to alterations in intracranial pressure, whether elevated (e.g., idiopathic intracranial hypertension) or decreased (e.g., cerebrospinal fluid leak), may require more specific diagnostic testing and treatment. Finally, headache in patients with COVID-19 or long COVID-19 is increasingly recognized and may have multiple etiologies.

Large artery intracranial stenosis in young adults with ischaemic stroke

Large artery intracranial stenosis (ICS) is a common finding in stroke patients, but is much less prevalent in Western countries than in Asia and in young adults than in the elderly. We investigated the prevalence and causes of ICS among French young adults with ischaemic stroke. Clinical and radiological data of patients aged 18-54 years treated consecutively for acute ischaemic stroke in the anterior circulation at a tertiary stroke centre were analysed retrospectively. Patients with>50% ICS were identified. ICS was evaluated using TOF-MRA, vessel wall-MRI, digital subtraction angiography and CT-angiography. A total of 316 patients were included. ICS was diagnosed in 29 patients, resulting in a prevalence of 9.2% (95% CI, 6.2 to 13.3). The leading cause of ICS was atherosclerosis (n=13), ahead of moyamoya disease (n=4), dissection (n=2), vasculitis (n=2), and reversible cerebral vasoconstriction syndrome (n=1). The cause of ICAS could not be determined in 7 patients. ICS was found in nearly one in 10 ischaemic strokes among French young adults. Atherosclerosis was the leading cause of ICS. The cause of ICS could not be determined in almost a quarter of the patients.

Reversible cerebral vasoconstriction syndrome associated with tetrodotoxin poisoning: A case report

An 81-year-old woman with a history of hypertension and Alzheimer's disease presented to the emergency department because of impaired consciousness. Physical examination revealed acute progressive generalized flaccid paralysis, hypertension, respiratory failure, and pupillary dilation. Although the patient did not complain of headache, head magnetic resonance angiography and magnetic resonance imaging showed multifocal segmental cerebral vasospasm and cerebral infarction in the left occipital lobe. Her family reported that although she did not have a license to cook pufferfish, she was in the habit of eating pufferfish. We subsequently detected tetrodotoxin in the patient's urine, and she was diagnosed with tetrodotoxin poisoning. As the symptoms of tetrodotoxin intoxication improved, head magnetic resonance angiography showed the disappearance of the multifocal segmental cerebral vasospasm. The patient's clinical course and imaging findings were consistent with reversible cerebral vasoconstriction syndrome (RCVS). Sympathetic overactivity after tetrodotoxin intoxication possibly caused the development of RCVS, and RCVS could not be ruled out even in the absence of the typical thunderclap headache. Magnetic resonance angiography is a useful modality when performing repeated examinations.

Type of headache at onset and risk for complications in reversible cerebral vasoconstriction syndrome

BACKGROUND

In a recent Italian study, 30% of patients with reversible cerebral vasoconstriction syndrome (RCVS) presented without thunderclap headache (TCH), and tended to present more severe forms of RCVS than patients with TCH. We aimed to analyze the risk for complications of RCVS in patients with and without TCH at onset.

METHODS

In a pooled cohort of 345 French patients with RCVS, we compared patients with and without TCH at onset regarding rates of neurological complications, and the functional outcome at 3 months.

RESULTS

As compared to the 281 patients with TCH at onset, the 64 patients without TCH had a higher risk for any neurological complication (61% vs. 24%, OR 4.9, 95% CI 2.8-8.7, p < 0.001). The association was strongest for cervical artery dissections (28% vs. 5%, OR 8.1, 95% CI 3.7-17.6, p < 0.001), followed by posterior reversible encephalopathy syndrome (17% vs. 3%, OR 7.1, 95% CI 2.7-18.4, p < 0.001), seizures (9% vs. 2.5%, OR 4.1, 95% CI 1.3-12.5, p = 0.019), and subarachnoid hemorrhage (41% vs. 16%, OR 3.5, 95% CI 1.9-6.3, p < 0.001). In multivariable analysis, the risk for any neurological complication remained significantly elevated in the absence of TCH (OR 3.5, 95% CI 1.8-6.8, p < 0.001). The functional outcome was equal in both groups, with a modified Rankin scale score of 0-1 in ≥90% of patients.

CONCLUSIONS

Absence of TCH at onset might predict a higher risk of complications in RCVS. Our results warrant further multicentric studies to prove this finding.

Cannabis and Inflammation in HIV: A Review of Human and Animal Studies

Persistent inflammation occurs in people with HIV (PWH) and has many downstream adverse effects including myocardial infarction, neurocognitive impairment and death. Because the proportion of people with HIV who use cannabis is high and cannabis may be anti-inflammatory, it is important to characterize the impact of cannabis use on inflammation specifically in PWH. We performed a selective, non-exhaustive review of the literature on the effects of cannabis on inflammation in PWH. Research in this area suggests that cannabinoids are anti-inflammatory in the setting of HIV. Anti-inflammatory actions are mediated in many cases through effects on the endocannabinoid system (ECS) in the gut, and through stabilization of gut–blood barrier integrity. Cannabidiol may be particularly important as an anti-inflammatory cannabinoid. Cannabis may provide a beneficial intervention to reduce morbidity related to inflammation in PWH.

Reversible Cerebral Vasoconstriction Syndrome without Headache That Was Initially Suspected of Being Primary Angiitis of the Central Nervous System

A 48-year-old man had convulsions, and magnetic resonance angiography (MRA) showed diffuse constriction of the cerebral arteries. He was suspected of having primary angiitis of the central nervous system (PACNS) and treated with steroid for three days. The MRA abnormality disappeared after a week. After 69 days, he developed dizziness, and MRA revealed recurrence of cerebral artery stenosis. Nevertheless, the symptoms and abnormal MRA findings recovered promptly without treatment. He was diagnosed with reversible cerebral vasoconstriction syndrome (RCVS) without headache. This case suggests that RCVS should be a differential diagnosis in patients without headache whose MRA findings show multiple cerebral artery stenosis.

Marijuana use and pregnancy outcomes among women with hypertension in pregnancy

Background: Marijuana has vasoconstrictive properties and its use has been associated with increased blood pressure in the general population. Yet, there are limited data on marijuana use and adverse outcomes among women with hypertension in pregnancy, even though these disorders are associated with severe maternal and fetal morbidity and mortality. Since marijuana is currently the most commonly used illicit drug in pregnancy, there is an urgent need to better understand the potential association between marijuana use and hypertension in pregnancy.Objective: To determine the adverse prenatal effects of marijuana use in women with hypertension in pregnancy.Study design: We conducted a retrospective cohort study among individuals with hypertension in pregnancy that delivered ≥23 weeks' gestation at Oregon Health & Science University (October 2013-September 2018). The primary exposure assessed was marijuana use, identified by chart review of documented patient self-report or positive urine toxicology screen. Individuals were stratified into two groups by marijuana use: use during pregnancy versus never used. Primary outcomes included composite adverse maternal and neonatal outcomes. Secondary outcomes included individual maternal outcomes, rarer neonatal outcomes and severe features of preeclampsia. Differences were analyzed by Fisher's exact, t-test, and logistic regression. Significance was determined by alpha = 0.05 for primary outcomes and alpha = 0.01 for secondary outcomes.Results: From 11,825 deliveries, 1,613 (13.6%) were classified with hypertension in pregnancy. A total of 117 individuals (7.3%) used marijuana during pregnancy, 1,110 (68.2%) had never used marijuana and 396 (24.6%) had unknown marijuana use and were excluded, leaving 1,217 individuals in this analysis. Women using marijuana in pregnancy were more likely to be younger, non-Hispanic White, publicly insured and using other substances compared to women who did not use marijuana. There were no differences in the overall distribution of hypertensive disorders, including preeclampsia with severe features, in women who used marijuana versus those who did not (p = .80). In multivariable analyses, after adjusting for maternal factors and other substance use, marijuana use was not associated with adverse maternal (aOR 1.23, 95% CI 0.43-3.50, p = .69) or neonatal (aOR 0.90, 95% CI 0.28-2.89, p = .86) outcomes.Conclusions: Marijuana use in pregnancy was not associated with maternal or neonatal outcomes or worsened hypertensive disease among women with hypertension in pregnancy after adjusting for maternal characteristics, including use of other substances. Our data highlight the need to consider use of other substances when evaluating the association between marijuana use in pregnancy and adverse pregnancy outcomes.

Assessing the public health impacts of legalizing recreational cannabis use: the US experience

The sale of cannabis for adult recreational use has been made legal in nine US states since 2012, and nationally in Uruguay in 2013 and Canada in 2018. We review US research on the effects of legalization on cannabis use among adults and adolescents and on cannabis-related harms; the impact of legalizing adult recreational use on cannabis price, availability, potency and use; and regulatory policies that may increase or limit adverse effects of legalization. The legalization of recreational cannabis use in the US has substantially reduced the price of cannabis, increased its potency, and made cannabis more available to adult users. It appears to have increased the frequency of cannabis use among adults, but not so far among youth. It has also increased emergency department attendances and hospitalizations for some cannabis-related harms. The relatively modest effects on cannabis use to date probably reflect restrictions on the number and locations of retail cannabis outlets and the constraints on commercialization under a continued federal prohibition of cannabis. Future evaluations of legalization should monitor: cannabis sales volumes, prices and content of tetrahydrocannabinol; prevalence and frequency of cannabis use among adolescents and adults in household and high school surveys; car crash fatalities and injuries involving drivers who are cannabis-impaired; emergency department presentations related to cannabis; the demand for treatment of cannabis use disorders; and the prevalence of regular cannabis use among vulnerable young people in mental health services, schools and the criminal justice system. Governments that propose to legalize and regulate cannabis use need to fund research to monitor the impacts of these policy changes on public health, and take advantage of this research to develop ways of regulating can-nabis use that minimize adverse effects on public health.

Harmful Effects of Smoking Cannabis: A Cerebrovascular and Neurological Perspective

Apart from being used as a medicine, cannabis or marijuana is the most widely abused recreational drug all over the world. The legalization and decriminalization of cannabis in Canada and various states of USA may be the underlying reason of the widespread popularity of it among young population. Various studies have reported about the relationship between cannabis use and different detrimental effects like cardiovascular, cerebrovascular, and neurological complications among different age groups. Specifically, the young population is getting adversely affected by this, harmful yet, readily accessible recreational drug. Although the mechanism behind cannabis mediated neurological and cerebrovascular complications has not been elucidated yet, the results of these studies have confirmed the association of these diseases with cannabis. Given the lack of comprehensive study relating these harmful complications with cannabis use, the aim of this narrative literature review article is to evaluate and summarize current studies on cannabis consumption and cerebrovascular/neurological diseases along with the leading toxicological mechanisms.

Avoiding Misdiagnosis in Patients With Posterior Circulation Ischemia: A Narrative Review

Posterior circulation strokes represent 20% of all acute ischemic strokes. Posterior circulation stroke patients are misdiagnosed twice as often compared to those with anterior events. Misdiagnosed patients likely have worse outcomes than correctly diagnosed patients because they are at risk for complications of the initial stroke as well as recurrent events due to lack of secondary stroke prevention and failure to treat the underlying vascular pathology. Understanding important anatomic variants, the clinical presentations, relevant physical examination findings, and the limitations of acute brain imaging may help reduce misdiagnosis. We present a symptom-based review of posterior circulation ischemia focusing on the subtler presentations with a brief discussion of basilar stroke, both of which can be missed by the emergency physician. Strategies to avoid misdiagnosis include establishing an abrupt onset of symptoms, awareness of the nonspecific presentations, consideration of basilar stroke in altered patients and using a modern approach to diagnosis of the acutely dizzy patient.

A Mechanistic and Pathophysiological Approach for Stroke Associated with Drugs of Abuse

Drugs of abuse are associated with stroke, especially in young individuals. The major classes of drugs linked to stroke are cocaine, amphetamines, heroin, morphine, cannabis, and new synthetic cannabinoids, along with androgenic anabolic steroids (AASs). Both ischemic and hemorrhagic stroke have been reported due to drug abuse. Several common mechanisms have been identified, such as arrhythmias and cardioembolism, hypoxia, vascular toxicity, vascular spasm and effects on the thrombotic mechanism, as causes for ischemic stroke. For hemorrhagic stroke, acute hypertension, aneurysm formation/rupture and angiitis-like changes have been implicated. In AAS abuse, the effect of blood pressure is rather substance specific, whereas increased erythropoiesis usually leads to thromboembolism. Transient vasospasm, caused by synthetic cannabinoids, could lead to ischemic stroke. Opiates often cause infective endocarditis, resulting in ischemic stroke and hypereosinophilia accompanied by pyogenic arthritis, provoking hemorrhagic stroke. Genetic variants are linked to increased risk for stroke in cocaine abuse. The fact that case reports on cannabis-induced stroke usually refer to the young population is very alarming.

A Systematic Review of the Complex Effects of Cannabinoids on Cerebral and Peripheral Circulation in Animal Models

While cannabis is perceived as a relatively safe drug by the public, accumulating clinical data suggest detrimental cardiovascular effects of cannabinoids. Cannabis has been legalized in several countries and jurisdictions recently. Experimental studies specifically targeting cannabinoids' effects on the cerebral vasculature are rare. There is evidence for transient vasoconstrictive effects of cannabinoids in the peripheral and cerebral vasculature in a complex interplay of vasodilation and vasoconstriction. Vasoreactivity to cannabinoids is dependent on the specific molecules, their metabolites and dose, baseline vascular tone, and vessel characteristics as well as experimental conditions and animal species. We systematically review the currently available literature of experimental results in in vivo and in vitro animal studies, examining cannabinoids' effects on circulation and reactive vasodilation or vasoconstriction, with a particular focus on the cerebral vascular bed.

Reversible cerebral vasoconstriction syndrome: an important and common cause of thunderclap and recurrent headaches

Reversible cerebral vasoconstriction syndrome is an intracranial vascular manifestation of a wide variety of diseases. It is the second most common cause of thunderclap headache, the most common cause of recurrent severe secondary headaches, and, in patients <60 years of age, has been reported as the commonest cause of isolated convexity subarachnoid haemorrhage. Radiologically, its key feature is vasoconstriction of the intracranial vessels, a dynamic process that is typically maximal at 2 weeks, varies in its distribution over the course of the disease, and typically resolves after 3 months. It can have haemorrhagic and ischaemic complications and sometimes occurs in concert with posterior reversible encephalopathy syndrome. It also has important associations with dissection and migraine. Rarer atypical cases can present with mild headache, no headache at all, or even a comatose state. This paper provides a detailed review of this syndrome, its pathophysiology, differential diagnosis, imaging findings, and work-up. It also describes the role that high-resolution magnetic resonance imaging (MRI) techniques can have in diagnosing the disease and emphasises the central role that all radiologists have in detecting this important and underdiagnosed condition.

Role of cannabis in cardiovascular disorders

The growing popularity of medical and recreational consumption of cannabis, especially among the youth, raises immediate concerns regarding its safety and long-terms effects. The cardiovascular effects of cannabis are not well known. Cannabis consumption has been shown to cause arrhythmia including ventricular tachycardia, and potentially sudden death, and to increase the risk of myocardial infarction (MI). These effects appear to be compounded by cigarette smoking and precipitated by excessive physical activity, especially during the first few hours of consumption. Cannabinoids, or the active compounds of cannabis, have been shown to have heterogeneous effects on central and peripheral circulation. Acute cannabis consumption has been shown to cause an increase in blood pressure, specifically systolic blood pressure (SBP), and orthostatic hypotension. Cannabis use has been reported to increase risk of ischemic stroke, particularly in the healthy young patients. The endocannabinoid system (ECS) is currently considered as a promising therapeutic target in the management of several disease conditions. Synthetic cannabinoids (SCs) are being increasingly investigated for their therapeutic effects; however, the value of their benefits over possible complications remains controversial. Despite the considerable research in this field, the benefits of cannabis and its synthetic derivatives remains questionable even in the face of an increasingly tolerating attitude towards recreational consumption and promotion of the therapeutic complications. More efforts are needed to increase awareness among the public, especially youth, about the cardiovascular risks associated with cannabis use and to disseminate the accumulated knowledge regarding its ill effects.

Recovery from spinal cord infarction associated with cannabis use

CONTEXT

Cerebrovascular and cardiovascular accidents have been associated with illicit drug use. The most commonly used substance worldwide is cannabis. It has been related to acute ischemic cerebral stroke in multiple reports, with different mechanisms suggested.

FINDINGS

This is a case of Acute Spinal Cord Ischemia Syndrome (ASCIS) in a 25-year-old male who presented 20 minutes after smoking cannabis. Although a direct causal relationship between cannabis and cerebrovascular accidents is difficult to establish, there might be an association.

CONCLUSION

The presented patient didn't have any vascular risk factors, and his symptoms started 20 minutes after smoking cannabis. This signifies a possible association between ASCIS and cannabis use.

Strokes are possible complications of cannabinoids use

It is critically important to identify all factors that may play a role in the recent increase of the incidence of stroke among the young population. Considering the worldwide use of cannabinoids (cannabis and synthetic cannabinoids), the recent legalization of their consumption in some countries, and their supposed involvement in cardiovascular events, we evaluated their role in the occurrence of neurovascular complications among the young. Ninety-eight patients were described in the literature as having a cannabinoids-related stroke (85 after cannabis use and 13 after synthetic cannabinoids). The distribution by type of stroke was as follows: 4 patients with an undetermined type of stroke, 85 with an ischemic stroke and/or a transient ischemic attack, and 9 with a hemorrhagic stroke. The mean age of patients was 32.3±11.8years (range 15-63), and the majority of them were male with a sex ratio of 3.7:1. Cannabis was often smoked with tobacco in 66% of cases. Most of the patients with cannabinoids-related strokes were chronic cannabis users in 81% of cases, and for 18% of them, there was a recent increase of the amount of cannabis consumption during the days before the occurrence of stroke. Even if the prognosis of stroke was globally favorable in 46% of cases, with no or few sequelae, 5 patients died after the neurovascular event. One striking element reported in the majority of the reports was a temporal relationship between cannabinoids use, whether natural or synthetic, and the occurrence of stroke. However, a temporal correlation does not mean causation, and other factors may be involved. Cannabis may be considered as a risk factor of stroke until research shows evidence of an underlying mechanism that, alone or in association with others, contributes to the development of stroke. As of today, reversible cerebral vasoconstriction triggered by cannabinoids use may be a convincing mechanism of stroke in 27% of cases. Indeed, despite the widespread use of cannabinoids, the low frequency of neurovascular complications after their use may be due to a genetic predisposition to their neurovascular toxicity in some individuals. Further studies should focus on this point. More importantly however, this low frequency may be underestimated because the drug consumption may not be systematically researched, neither by questioning nor by laboratory screening. Besides this vascular role of cannabinoids in the occurrence of stroke, a cellular effect of cannabis on brain mitochondria was recently suggested in an experimental study. One of the mechanisms involved in young cannabis users with stroke may be the generation of reactive oxygen species leading to an oxidative stress, which is a known mechanism in stroke in humans. It is useful to inform the young population about the real potential risk of using cannabinoids. We suggest to systematically ask all young adults with stroke about their drug consumption including cannabinoids, to screen urine for cannabis or to include a specific diagnostic test to detect synthetic cannabinoids, and to obtain non-invasive intracranial arterial investigations (i.e. CT-angiography or cerebral MRA) in order to search for cerebral vasoconstriction. However, several questions remained unresolved and further research is still needed to assess the pathophysiological mechanisms involved in young cannabinoids users with stroke. This article is part of a Special Issue entitled "Cannabinoids and Epilepsy".

Cannabis, Tobacco, Alcohol Use, and the Risk of Early Stroke: A Population-Based Cohort Study of 45 000 Swedish Men

BACKGROUND AND PURPOSE

Current knowledge on cannabis use in relation to stroke is based almost exclusively on clinical reports. By using a population-based cohort, we aimed to find out whether there was an association between cannabis use and early-onset stroke, when accounting for the use of tobacco and alcohol.

METHODS

The cohort comprises 49 321 Swedish men, born between 1949 and 1951, who were conscripted into compulsory military service between the ages of 18 and 20. All men answered 2 detailed questionnaires at conscription and were subject to examinations of physical aptitude, psychological functioning, and medical status. Information on stroke events up to ≈60 years of age was obtained from national databases; this includes strokes experienced before 45 years of age.

RESULTS

No associations between cannabis use in young adulthood and strokes experienced ≤45 years of age or beyond were found in multivariable models: cannabis use >50 times, hazard ratios=0.93 (95% confidence interval [CI], 0.34-2.57) and 0.95 (95% CI, 0.59-1.53). Although an almost doubled risk of ischemic stroke was observed in those with cannabis use >50 times, this risk was attenuated when adjusted for tobacco usage: hazards ratio=1.47 (95% CI, 0.83-2.56). Smoking ≥20 cigarettes per day was clearly associated both with strokes before 45 years of age, hazards ratio=5.04 (95% CI, 2.80-9.06), and with strokes throughout the follow-up, hazards ratio=2.15 (95% CI, 1.61-2.88).

CONCLUSIONS

We found no evident association between cannabis use in young adulthood and stroke, including strokes before 45 years of age. Tobacco smoking, however, showed a clear, dose-response shaped association with stroke.

Alcohol and cannabis: Comparing their adverse health effects and regulatory regimes

The claim that the adverse health effects of cannabis are much less serious than those of alcohol has been central to the case for cannabis legalisation. Regulators in US states that have legalised cannabis have adopted regulatory models based on alcohol. This paper critically examines the claim about adverse health effects and the wisdom of regulating cannabis like alcohol. First, it compares what we know about the adverse health effects of alcohol and cannabis. Second, it discusses the uncertainties about the long term health effects of sustained daily cannabis use. Third, it speculates about how the adverse health effects of cannabis may change after legalisation. Fourth, it questions the assumption that alcohol provides the best regulatory model for a legal cannabis market. Fifth, it outlines the major challenges in regulating cannabis under the liberal alcohol-like regulatory regimes now being introduced.

Evaluating the public health impacts of legalizing recreational cannabis use in the United States

BACKGROUND AND AIMS

Since 2012 four US states have legalized the retail sale of cannabis for recreational use by adults, and more are likely to follow. This report aimed to (1) briefly describe the regulatory regimes so far implemented; (2) outline their plausible effects on cannabis use and cannabis-related harm; and (3) suggest what research is needed to evaluate the public health impact of these policy changes.

METHOD

We reviewed the drug policy literature to identify: (1) plausible effects of legalizing adult recreational use on cannabis price and availability; (2) factors that may increase or limit these effects; (3) pointers from studies of the effects of legalizing medical cannabis use; and (4) indicators of cannabis use and cannabis-related harm that can be monitored to assess the effects of these policy changes.

RESULTS

Legalization of recreational use will probably increase use in the long term, but the magnitude and timing of any increase is uncertain. It will be critical to monitor: cannabis use in household and high school surveys; cannabis sales; the number of cannabis plants legally produced; and the tetrahydrocannabinol (THC) content of cannabis. Indicators of cannabis-related harms that should be monitored include: car crash fatalities and injuries; emergency department presentations; presentations to addiction treatment services; and the prevalence of regular cannabis use among young people in mental health services and the criminal justice system.

CONCLUSIONS

Plausible effects of legalizing recreational cannabis use in the United States include substantially reducing the price of cannabis and increasing heavy use and some types of cannabis-related harm among existing users. In the longer term it may also increase the number of new users.