Transient ischemic attack in heavy cannabis smokers--how 'safe' is it?

Cannabis and Lung Health: Does the Bad Outweigh the Good?

Cannabis use is growing, with multiple medical ‘indications’ and approval for recreational use in many countries. This article will review some of the respiratory complications to cannabis use, which include lung function changes, lung destruction, increased risk of lung and head and neck cancer, and others. These are mostly related to smoking, and the co-administration of nicotine makes the risks a bit difficult to measure. However, with many reports of EVALI, electronic vaping-associated lung injury, being related to cannabis coadministration, it appears that the safest administration of cannabis, as far as lung health, is orally.

Case Report: Spontaneous simultaneous coronary and carotid dissection in a young cannabis user

Due to legalization of its consumption in some countries and its medical use as well as low toxic potential, cannabis remains the most widely used drug around the world and the rate of usage is only increasing.  Nevertheless, there are several case reports of vascular complications following cannabis use even in young people without cardiovascular risk factors. We report the case of a cannabis smoker presenting to the emergency room for an ischemic stroke associated with an acute coronary syndrome related to a spontaneous simultaneous double dissection of the carotid artery and the left anterior descending artery, with a favourable outcome under medical treatment. This case shows the seriousness of complications due to the cannabis consumption, hence the need to limit or even prohibit its consumption.

Stroke and cannabis use in patients with no cardiovascular risk factors: a systematic review of case reports

INTRODUCTION

Cannabis and its synthetic analogues are currently the most widely consumed illicit substances worldwide. Multiple alterations have been linked to its use, including cerebrovascular disease (CVD) or stroke, whose association with the substance has been based mainly on the hypothesis of transient vasoconstriction, which explains a large proportion of the cases reported. However, epidemiological studies have not performed an individual analysis of patients without other cardiovascular risk factors, which may limit the estimation of the risk of stroke associated with cannabis use alone.

DEVELOPMENT

A systematic literature review was conducted through Medline, EBSCOhost, EMBASE, Lilacs, and Scielo to gather case reports published before 13 May 2016 presenting patients with a diagnosis of CVD or transient ischaemic attack, a history of cannabinoid use, and no other cardiovascular risk factors. Key words such as stroke, cerebrovascular disease, cannabis, and marijuana, among others, were used. A total of 18 case reports were selected from the 566 references found.

CONCLUSIONS

There is a wide variety of reports of stroke associated with cannabis use in patients with no other risk factors. Noteworthy findings were presentation at young age and a strong temporal association, which place cannabis use as a potential risk factor for this population in line with the epidemiological and pathophysiological studies in this area.

Reevaluating America's Latest Pharmaceutical Trend: The Cardiovascular Risk of Cannabis

For the first time in the history of the modern era smoking tobacco is not the most popular inhaled product. After a flurry of legislature, cannabis has come to the forefront of both medicinal and recreational drug use. A confluence of evidence suggests, however, that marijuana consumption may confer a particularly worrisome cardiovascular risk profile. While combustible forms still contain many of the same harmful chemicals found in tobacco such as aromatic amines, polycyclic aromatic hydrocarbons (PAHs), and nitric oxide, some in even greater concentrations than tobacco, edible preparations have been evidenced to cause more cardiovascular-related emergency department visits. Importantly, this body of evidence suggests that cannabis use may be placing a younger, healthier population at risk of suffering major cardiovascular accidents particularly in the moments immediately following consumption. With males in their 30's apparently bearing the brunt of this burden, cannabis consumption has been associated with an increase in ischemic stroke-a blockage in the cerebral or cerebellar vasculature-and almost a fivefold increase in myocardial infarction. THC containing compounds have also been linked to vascular complications ranging from mild plaques to total arterial occlusion resulting in claudication, rest pain, ischemic ulceration and gangrene-recently termed cannabis arteritis. While this research remains in a nascent stage, marijuana consumption seems to be predisposing a youthful, traditionally low health risk cohort to a variety of major adverse cardiovascular events.

Disseminated Intravascular Coagulopathy Secondary to Unintentional Brodifacoum Poisoning via Synthetic Marijuana

Recent evidence demonstrates a rising epidemic of unintentional brodifacoum poisoning associated with synthetic cannabinoid use. Synthetic cannabinoid use is on the rise because of its inexpensiveness as well as difficulty to screen and regulate. We present a rare case of severe coagulopathy and cardiac arrest secondary to synthetic cannabinoid use complicated by brodifacoum toxicity.

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.

Cardiovascular Complications of Marijuana and Related Substances: A Review

The recreational use of cannabis has sharply increased in recent years in parallel with its legalization and decriminalization in several countries. Commonly, the traditional cannabis has been replaced by potent synthetic cannabinoids and cannabimimetics in various forms. Despite overwhelming public perception of the safety of these substances, an increasing number of serious cardiovascular adverse events have been reported in temporal relation to recreational cannabis use. These have included sudden cardiac death, vascular (coronary, cerebral and peripheral) events, arrhythmias and stress cardiomyopathy among others. Many of the victims of these events are relatively young men with few if any cardiovascular risk factors. However, there are reasons to believe that older individuals and those with risk factors for or established cardiovascular disease are at even higher danger of such events following exposure to cannabis. The pathophysiological basis of these events is not fully understood and likely encompasses a complex interaction between the active ingredients (particularly the major cannabinoid, Δ9-tetrahydrocannabinol), and the endo-cannabinoid system, autonomic nervous system, as well as other receptor and non-receptor mediated pathways. Other complicating factors include opposing physiologic effects of other cannabinoids (predominantly cannabidiol), presence of regulatory proteins that act as metabolizing enzymes, binding molecules, or ligands, as well as functional polymorphisms of target receptors. Tolerance to the effects of cannabis may also develop on repeated exposures at least in part due to receptor downregulation or desensitization. Moreover, effects of cannabis may be enhanced or altered by concomitant use of other illicit drugs or medications used for treatment of established cardiovascular diseases. Regardless of these considerations, it is expected that the current cannabis epidemic would add significantly to the universal burden of cardiovascular diseases.

Medical Marijuana: Current Concepts, Pharmacological Actions of Cannabinoid Receptor Mediated Activation, and Societal Implications

PURPOSE OF REVIEW

The purpose of the following review is to summarize the history and current policies related to marijuana use and prevalence, basic and clinical science pharmacological literature regarding efficacy, subpopulations of concern, and varying policies regarding its use at present.

RECENT FINDINGS

With the increasingly widespread utilization of marijuana, there is also a growing complexity of public health policy, regulation, and necessity to further assess the medical indications and adverse long-term effects of marijuana use. Health care providers as well as the general public must be prepared to become familiar and up-to-date with medical literature, legislation, and educational material regarding medical marijuana.

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".

Neurotoxicology and drug-related disorders

Neuropsychiatric disorders caused by toxic substances pose a great diagnostic challenge due to the large variety of changes caused in the central and peripheral nervous system. The pathogenetic mechanisms at work are multifaceted and partly not solved. In human drug abusers (cannabis, opiates, cocaine, amphetamines, methamphetamine and "designer drugs"), a broad spectrum of central nervous system alterations are observed including infarction, intracerebral and subarachnoidal hemorrhage, hypoxic-ischemic leukoencephalopathy, infections, neuronal loss, specific astroglial and microglial reaction patterns, and vascular changes, including the endothelial cell as well as the basal lamina.

Progress toward pharmacotherapies for cannabis-use disorder: an evidence-based review

Cannabis is the most widely used and variably regulated drug in the world, with increasing trends of use being reported in the US, Australia, Asia, and Africa. Evidence has shown a decrease in the age of commencement of cannabis use in some developed countries and a prolongation of risk of initiation to cannabis use beyond adolescence among more recent users. Cannabis use is associated with numerous health risks and long-term morbidity, as well as risk of developing cannabis-use disorders. Cannabis users infrequently seek professional treatment, and normally do so after a decade of use. Cannabis-use disorders are currently treated using a selection of psychosocial interventions. Severity of withdrawal is a factor that increases the risk of relapse, and is the target of pharmacotherapy studies. Currently, there is no approved pharmacotherapy for cannabis-use disorders. A number of approaches have been examined, and trials are continuing to find a safe and effective medication with little abuse liability.

Cannabis and stroke: systematic appraisal of case reports

BACKGROUND AND PURPOSE

An increasing number of case reports link cannabis consumption to cerebrovascular events. Yet these case reports have not been scrutinized using criteria for causal inference.

METHODS

All case reports on cannabis and cerebrovascular events were retrieved. Four causality criteria were addressed: temporality, adequacy of stroke work-up, effects of rechallenge, and concomitant risk factors that could account for the cerebrovascular event.

RESULTS

There were 34 case reports on 64 patients. Most cases (81%) exhibited a temporal relationship between cannabis exposure and the index event. In 70%, the evaluation was sufficiently comprehensive to exclude other sources for stroke. About a quarter (22%) of patients had another stroke after subsequent re-exposure to cannabis. Finally, half of patients (50%) had concomitant stroke risk factors, most commonly tobacco (34%) and alcohol (11%) consumption.

CONCLUSIONS

Many case reports support a causal link between cannabis and cerebrovascular events. This accords well with epidemiological and mechanistic research on the cerebrovascular effects of cannabis.

Cannabis and cardiotoxicity

Cannabis is the most commonly consumed illicit drug. It is estimated that 4% of the global population between the ages of 15 and 64 smoked marijuana in 2003. Despite the drug's extreme popularity, reports of cannabis-related stroke and myocardial infarction are so rare as to still be reportable. Cannabinoids, the active compounds contained in marijuana, interact with cardiovascular centers in the brain, but also exert direct effects on vascular tone. Recent animal and in vitro studies have yielded conflicting results, some suggesting minimal effect, others suggesting that cannabinoids may be potent myocardial depressants. The observation that cardiotoxicity has never been reported in cancer patients taking dronabinol, the synthetic form of THC, tends to suggest that animal studies may have overstated the cardiovascular risk, which is probably comparable to that of smoking cigarettes.

Emergence of new classes of recreational drugs-synthetic cannabinoids and cathinones

Designer drugs represent an increasingly popular form of recreational substance abuse, especially amongst young adults. The two classes of designer drugs that have recently risen to prominence are the synthetic cannabinoids and synthetic cathinones. These substances are not detected by conventional drug screening methods and can often be associated with serious health consequences, including seizures, renal failure and death. Thus, clinicians should be familiar with the signs, symptoms, and toxicities associated with the use of these substances, and maintain a high level of suspicion for synthetic drugs as an alternative means of "getting high." We present a case of a 20-year-old college student who presented to the emergency department with altered mental status and severe agitation who later admitted to using bath salts. The goal of this article is to raise awareness about these new designer drugs, their clinical presentation, and management of their intoxication.

Adverse cardiovascular, cerebrovascular, and peripheral vascular effects of marijuana inhalation: what cardiologists need to know

Marijuana is the most widely used illicit drug, with approximately 200 million users worldwide. Once illegal throughout the United States, cannabis is now legal for medicinal purposes in several states and for recreational use in 3 states. The current wave of decriminalization may lead to more widespread use, and it is important that cardiologists be made aware of the potential for marijuana-associated adverse cardiovascular effects that may begin to occur in the population at a greater frequency. In this report, the investigators focus on the known cardiovascular, cerebrovascular, and peripheral effects of marijuana inhalation. Temporal associations between marijuana use and serious adverse events, including myocardial infarction, sudden cardiac death, cardiomyopathy, stroke, transient ischemic attack, and cannabis arteritis have been described. In conclusion, the potential for increased use of marijuana in the changing legal landscape suggests the need for the community to intensify research regarding the safety of marijuana use and for cardiologists to maintain an awareness of the potential for adverse effects.

Acute intoxication caused by a synthetic cannabinoid in two adolescents

Illicit drug use continues to be a common problem among pediatric patients. Daily marijuana use among high school seniors is currently at a 30-year high. Marijuana use in adults has rarely been associated with cardiovascular adverse effects, including hypertension, tachycardia, arrhythmia, and myocardial infarction. Recently, abuse of synthetic cannabinoids, such as the incense "K2" or "Spice," has been increasingly reported in the lay press and medical literature. Overdose and chronic use of these substances may cause adverse effects including altered mental status, tachycardia, and loss of consciousness. Overdoses in adult patients have been described; however, limited reports in the pediatric population have been documented. A recent case series describes myocardial infarctions in pediatric patients, associated with synthetic cannabinoid use. In this report, we describe two adolescent patients admitted after they inhaled "K2," resulting in loss of consciousness, tachycardia, and diffuse pain.

Epidemic of illicit drug use, mechanisms of action/addiction and stroke as a health hazard

Drug abuse robs individuals of their jobs, their families, and their free will as they succumb to addiction; but may cost even more: a life of disability or even life lost due to stroke. Many illicit drugs have been linked to major cardiovascular events and other comorbidities, including cocaine, amphetamines, ecstasy, heroin, phencyclidine, lysergic acid diethylamide, and marijuana. This review focuses on available epidemiological data, mechanisms of action, particularly those leading to cerebrovascular events, and it is based on papers published in English in PubMed during 1950 through February 2011. Each drug's unique interactions with the brain and vasculature predispose even young, healthy people to ischemic or hemorrhagic stroke. Cocaine and amphetamines have the strongest association with stroke. However, the level of evidence firmly linking other drugs to stroke pathogenesis is weak. Large epidemiological studies and systematic evaluation of each drug's action on the brain and cardiovascular system are needed to reveal the full impact of drug use on the population.

Medical marijuana and the developing role of the pharmacist

PURPOSE

The pharmacology, therapeutic uses, safety, drug-drug interactions, and drug-disease interactions of medical marijuana are reviewed, and the legal issues related to its use and the implications of medical marijuana for the pharmacist are presented.

SUMMARY

Marijuana contains more than 460 active chemicals and over 60 unique cannabinoids. The legal landscape surrounding marijuana is surprisingly complex and unsettled. In the United States, 11 states and several municipalities have legalized medical marijuana. Another state provides legislation that allows patients to claim a defense of medical necessity. Nevertheless, patients using medical marijuana may never interact with a pharmacist. Marijuana is a Schedule I controlled substance and its use is illegal under federal law. Marijuana has a number of purported therapeutic uses with a broad range of supporting evidence. There are five general indications for medical marijuana: (1) severe nausea and vomiting associated with cancer chemotherapy or other causes, (2) weight loss associated with debilitating illnesses, including HIV infection and cancer, (3) spasticity secondary to neurologic diseases, such as multiple sclerosis, (4) pain syndromes, and (5) other uses, such as for glaucoma. Marijuana is associated with adverse psychiatric, cardiovascular, respiratory, and immunologic events. Moreover, marijuana may interact with a number of prescription drugs and concomitant disease states.

CONCLUSION

Several states have legalized the use of marijuana for chronic and debilitating medication conditions. Pharmacists need to understand the complex legal framework surrounding this issue so that they can protect themselves and better serve their patients.

Marijuana as a trigger of cardiovascular events: speculation or scientific certainty?

Marijuana is the most widely used illicit substance in the United States. Cardiovascular complications in association with marijuana use have been reported during the past three decades. In view of the elevated public interest in this drug's role in pharmacotherapy in the recent years and the aging population of long-term marijuana users from the late 1960s, encounters with marijuana-related cardiovascular adversities may be silently on the rise. The purpose of this article is to increase awareness of the potential of marijuana to lead to cardiovascular disease. Here, we will discuss the physiologic effects of marijuana and include a comprehensive review of the studies and case reports that provide supportive evidence for marijuana as a trigger of adverse cardiovascular events, including tachyarrhythmias, acute coronary syndrome, vascular complications, and even congenital heart defects.

Keep off the grass: marijuana use and acute cardiovascular events

Marijuana is one of the most widely used recreational substances in the world, considered by many consumers as a relatively safe drug with few significant side-effects. We report the case of a 21-year-old man who suffered an acute myocardial infarction following the use of marijuana, despite having no other identifiable risk factors for an acute cardiovascular event. We review the published medical literature regarding acute cardiovascular events following marijuana use and postulate a possible mechanism for this unusual pathological consequence of marijuana use.

Effects of marijuana on neurophysiological signals of working and episodic memory

RATIONALE

The primary psychoactive constituent of marijuana, Delta9-THC, activates cannabinoid receptors, which are especially abundant in the frontal cortex and hippocampus. Acute marijuana smoking can disrupt working memory (WM) and episodic memory (EM) functions that are known to rely on these regions. However, the effects of marijuana on the brain activity accompanying such cognitive processes remain largely unexplored.

OBJECTIVES

To examine such effects on performance and neurophysiological signals of these functions, EEG recordings were obtained from ten subjects (5M, 5F) performing cognitive tasks before and after smoking marijuana (3.45% Delta9-THC) or a placebo. WM was assessed with a spatial N-back task, and EM was evaluated with a test requiring recognition of words after a 5-10 min delay between study and test.

RESULTS

Marijuana increased heart rate and decreased global theta band EEG power, consistent with increased autonomic arousal. Responses in the WM task were slower and less accurate after smoking marijuana, accompanied by reduced alpha band EEG reactivity in response to increased task difficulty. In the EM task, marijuana was associated with an increased tendency to erroneously identify distracter words as having been previously studied. In both tasks, marijuana attenuated stimulus-locked event-related potentials (ERPs).

CONCLUSIONS

The results suggest that marijuana disrupted both sustained and transient attention processes resulting in impaired memory task performance. In subjects most affected by marijuana a pronounced ERP difference between previously studied words and new distracter words was also reduced, suggesting disruption of neural mechanisms underlying memory for recent study episodes.

Adverse effects of cannabis on health: an update of the literature since 1996

Recent research has clarified a number of important questions concerning adverse effects of cannabis on health. A causal role of acute cannabis intoxication in motor vehicle and other accidents has now been shown by the presence of measurable levels of Delta(9)-tetrahydrocannabinol (THC) in the blood of injured drivers in the absence of alcohol or other drugs, by surveys of driving under the influence of cannabis, and by significantly higher accident culpability risk of drivers using cannabis. Chronic inflammatory and precancerous changes in the airways have been demonstrated in cannabis smokers, and the most recent case-control study shows an increased risk of airways cancer that is proportional to the amount of cannabis use. Several different studies indicate that the epidemiological link between cannabis use and schizophrenia probably represents a causal role of cannabis in precipitating the onset or relapse of schizophrenia. A weaker but significant link between cannabis and depression has been found in various cohort studies, but the nature of the link is not yet clear. A large body of evidence now demonstrates that cannabis dependence, both behavioral and physical, does occur in about 7-10% of regular users, and that early onset of use, and especially of weekly or daily use, is a strong predictor of future dependence. Cognitive impairments of various types are readily demonstrable during acute cannabis intoxication, but there is no suitable evidence yet available to permit a decision as to whether long-lasting or permanent functional losses can result from chronic heavy use in adults. However, a small but growing body of evidence indicates subtle but apparently permanent effects on memory, information processing, and executive functions, in the offspring of women who used cannabis during pregnancy. In total, the evidence indicates that regular heavy use of cannabis carries significant risks for the individual user and for the health care system.

Cannabis use and cerebrovascular disease

BACKGROUND

Cannabis is the most commonly abused illicit drug and is often considered innocuous. However, cases of acute onset neurologic dysfunction occurring in relation to cannabis use have been described and corresponding cerebral imaging studies have documented focal ischemic changes and vessel abnormalities.

REVIEW SUMMARY

This article reviews all reported cases of presumed cannabis related cerebral ischemic events in the medical literature, as well as pertinent human and animal experimental studies on the cardiovascular and cerebrovascular effects of cannabis.

CONCLUSIONS

Cannabis use seems to have been causally related to several instances of cerebral ischemia and infarction. Proposed etiologic mechanisms have included cerebral vasospasm, cardioembolization, and systemic hypotension with impaired cerebral autoregulation, but most of the available data points to a vasospastic process. The exact relation of cannabis to cerebrovascular disease remains to be determined.

Are cannabinoid drugs neurotoxic or neuroprotective?

Chronic exposure to cannabinoids was shown to induce long lasting impairment of learning and memory, which was accompanied by morphological damage to the brain. On the other hand, several studies have shown that cannabinoids can protect from various brain traumas. This enigmatic dualism is explained herein by a comprehensive hypothesis, which is based on our recent in vitro studies and on pharmacokinetic in vivo considerations. The hypothesis predicts that low concentrations of cannabinoids will be neurotoxic while high concentrations of the drugs will protect from neuronal damage, and suggests that chronic administration of cannabinoids will induce neuronal death, while their acute administration will protect the brain. We further propose straight forward experiments, both in vivo (animal models for brain damage) and in vitro (cell death in neuronal cultures) to verify this hypothesis. The outcome of these experiments may have practical applications when considering the use of cannabinoids as therapeutic agents and in evaluating the consequences of their use as recreational drugs.

Cardiovascular consequences of marijuana use

This review describes what is known about effects of marijuana and cannabinoids in relation to human physiological and disease outcomes. The acute physiological effects of marijuana include a substantial dose-dependent increase in heart rate, generally associated with a mild increase in blood pressure. Orthostatic hypotension may occur acutely as a result of decreased vascular resistance. Smoking marijuana decreases exercise test duration in maximal exercise tests, increases the heart rate at submaximal levels of exercise. Tolerance develops to the acute effects of marijuana smoking and delta9-tetrahydrocannibol (THC) over several days to a few weeks. The cardiovascular responses that occur in response to THC are mediated by the autonomic nervous system, with recent findings also demonstrating that the human cannabinoid receptor system plays a role in regulating the cardiovascular response. Although several mechanisms exist by which marijuana use might contribute to the development of chronic cardiovascular conditions or acutely trigger cardiovascular events, there are few data regarding marijuana/THC use and cardiovascular disease outcomes. A large cohort study showed no association of marijuana use with cardiovascular disease hospitalization or mortality. However, acute effects of marijuana use include a decrease of the time until the onset of chest pain in patients with angina pectoris; one study has shown that marijuana may trigger the onset of myocardial infarction. Patients who have coronary heart disease or are at high risk for the development of CHD should be cautioned about the potential hazards of marijuana use as a precipitant for clinical events. Research directions might include more studies of cardiovascular disease outcomes and relationships of marijuana with cardiovascular risk factors, studies of metabolic and physiologic effects of chronic marijuana use that may affect cardiovascular disease risk, increased understanding of the role of the cannabinoid receptor system in cardiovascular regulation, and studies to determine if there is a therapeutic role for cannabinoids in blood pressure control or for neuroprotection after stroke.

Cardiovascular system effects of marijuana

Marijuana and delta9-tetrahydrocannabinol (THC) increase heart rate, slightly increase supine blood pressure, and on occasion produce marked orthostatic hypotension. Cardiovascular effects in animals are different, with bradycardia and hypotension the most typical response. Cardiac output increases, and peripheral vascular resistance and maximum exercise performance decrease. Tolerance to most of the initial cardiovascular effects appears rapidly. With repeated exposure, supine blood pressure decreases slightly, orthostatic hypotension disappears, blood volume increases, heart rate slows, and circulatory responses to exercise and Valsalva maneuver are diminished, consistent with centrally mediated, reduced sympathetic, and enhanced parasympathetic activity. Receptor-mediated and probably nonneuronal sites of action account for cannabinoid effects. The endocannabinoid system appears important in the modulation of many vascular functions. Marijuana's cardiovascular effects are not associated with serious health problems for most young, healthy users, although occasional myocardial infarction, stroke, and other adverse cardiovascular events are reported. Marijuana smoking by people with cardiovascular disease poses health risks because of the consequences of the resulting increased cardiac work, increased catecholamine levels, carboxyhemoglobin, and postural hypotension.

Marijuana use among adolescents

More than half of US adolescents will experiment with marijuana. Of those who try marijuana more than once, approximately one third will subsequently use marijuana regularly, although most will have stopped by their late 20s. Although genetic predisposition plays the most important role in determining who will develop dependence, environmental factors influence who will initiate marijuana use. One of the challenges for prevention and treatment programs is that the immediate adverse effects of marijuana use are not extreme, and many adolescents have difficulty in making decisions based on future risks. Therefore, the consequences of leaving school early, having unprotected sex, and driving while intoxicated are often insufficient to deter adolescents from using marijuana. Thus, it is not surprising that current prevention and treatment programs have had limited success in decreasing the rates of initiation and regular use of marijuana among adolescents. However, the accumulation of data about marijuana use in adolescents has the potential to enable the development of more effective prevention and treatment programs.