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A single dose of cannabidiol reduces blood pressure in healthy volunteers in a randomized crossover study 1 Division of Medical Sciences & Graduate Entry Medicine, University of Nottingham, Royal In recent years, CBD oil has been called the 'miracle of the modern age'. But what is CBD, and can CBD products help the heart? Marijuana is legal for medical use in more than half of the U.S. states. Although the cannabis plant has been used for thousands of years, reliable scientific research on its medical benefits and potential risks has lagged behind.

A single dose of cannabidiol reduces blood pressure in healthy volunteers in a randomized crossover study

1 Division of Medical Sciences & Graduate Entry Medicine, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom.

Garry D. Tan

2 The NIHR Oxford Biomedical Research Centre, Oxford Centre for Diabetes, Endocrinology & Metabolism, Churchill Hospital, Oxford University Hospitals NHS Trust, Oxford, United Kingdom.

Saoirse E. O’Sullivan

1 Division of Medical Sciences & Graduate Entry Medicine, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom.

1 Division of Medical Sciences & Graduate Entry Medicine, University of Nottingham, Royal Derby Hospital Centre, Derby, United Kingdom.

2 The NIHR Oxford Biomedical Research Centre, Oxford Centre for Diabetes, Endocrinology & Metabolism, Churchill Hospital, Oxford University Hospitals NHS Trust, Oxford, United Kingdom.

Associated Data

Abstract

BACKGROUND. Cannabidiol (CBD) is a nonpsychoactive phytocannabinoid used in multiple sclerosis and intractable epilepsies. Preclinical studies show CBD has numerous cardiovascular benefits, including a reduced blood pressure (BP) response to stress. The aim of this study was to investigate if CBD reduces BP in humans.

METHODS. Nine healthy male volunteers were given 600 mg of CBD or placebo in a randomized, placebo-controlled, double-blind, crossover study. Cardiovascular parameters were monitored using a finometer and laser Doppler.

CONCLUSIONS. This data shows that acute administration of CBD reduces resting BP and the BP increase to stress in humans, associated with increased HR. These hemodynamic changes should be considered for people taking CBD. Further research is required to establish whether CBD has a role in the treatment of cardiovascular disorders.

Introduction

Epidemiological studies have shown a positive relationship between long-term stress and the development of cardiovascular disease (1). Factors like social isolation, low socioeconomic status, depression, stressful family and work life, and anxiety are associated with an increased risk of the development and accelerated progression of existing cardiovascular disease. Current European guidelines on the prevention of cardiovascular disease have emphasized the importance of tackling these factors (2). Mental stress induces myocardial ischaemia in patients with stable coronary artery disease, and this appears to be mediated by adrenal release of catecholamines (3).

Cannabinoids (CBs) are compounds that bind to CB receptors or are structurally similar to compounds that bind to CB receptors. They include endogenously produced compounds (called endocannabinoids), synthetic compounds and phytocannabinoids obtained from the Cannabis sativa plant. There are over 80 known types of phytocannabinoids, the most widely studied of which is Δ 9 tetrahydrocannabinol (Δ 9 -THC or THC), which is responsible for the psychoactive properties of cannabis (4). The other major phytocannabinoid is cannabidiol (CBD), which does not have psychoactive properties. CBD is currently the focus of much research due to its potential in a number of therapeutic areas, as it has been shown to have antiinflammatory, anticonvulsant, antioxidant, anxiolytic, antinausea, and antipsychotic properties (5). A number of preclinical studies have also shown beneficial effects of CBD in a range of disorders of the cardiovascular system (6). A CBD/THC combination (Sativex/Nabiximols, GW Pharmaceuticals) is licensed for the treatment of spasticity in multiple sclerosis, and CBD alone (Epidiolex, GW Pharmaceuticals) has entered an expanded access program in children with intractable epilepsies (Dravet syndrome and Lennox-Gastaut syndrome). Epidiolex has also received orphan designation status for the treatment of neonatal hypoxia-ischaemic encephalopathy.

CBD has multiple desirable effects on the cardiovascular system. It attenuates high glucose–induced proinflammatory changes in human coronary artery endothelial cells (7) and myocardial dysfunction associated with animal models of diabetes (8), and it preserves endothelial integrity in diabetic retinal microvasculature (9). In vivo administration of CBD before cardiac ischemia and reperfusion also reduces ventricular arrhythmias and infarct size. CBD also causes both acute and time-dependent vasorelaxation in isolated arteries in rats and humans (10–12). There is also evidence from animal studies that CBD modulates the cardiovascular response to stress. Resstel and colleagues (13) showed in rats that i.p. injection of CBD (10 and 20 mg/kg, –30 min) reduced restraint stress–induced cardiovascular response and behavior. Both these effects were blocked by preadministration of WAY100635 (0.1 mg/kg), a 5-hydroxytryptamine 1A (5HT1A) antagonist. These effects appear to be mediated centrally and involve the bed nucleus of the stria terminalis (BNST), a limbic structure that modulates neuroendocrine responses to acute stress (14).

Our recent systematic review showed us that there are no dedicated studies in humans to date, to our knowledge, looking at the effect of CBD on either resting cardiovascular measurement or on the responses to stress, with continuous monitoring of CV parameters (15). Therefore, the aim of the present study was to investigate whether CBD decreases the cardiovascular response to stress after the administration of a single dose of CBD (600 mg) in healthy volunteers, with the hypothesis that blood pressure would be reduced by CBD. Noninvasive cardiovascular measurements were used along with stress tests in the form of mental arithmetic, isometric exercise, and the cold pressor test.

Results

Ten male subjects were recruited, but 1 withdrew for personal reasons. The mean age, weight, and height of the volunteers were 23.7 ± 3.2 years, 77.5 ± 6.4 kg, and 178.6 ± 4.5 cm (mean ± SD).

Effect of CBD on resting cardiovascular parameters.

Changes in resting cardiovascular parameters after a single dose (600 mg) of cannabidiol (CBD) in healthy volunteers (n = 9).

The effects of placebo (closed square) and CBD (open square) on systolic blood pressure (SBP) (A), diastolic blood pressure (DBP) (B), mean arterial blood pressure (MAP) (C), heart rate (HR) (D), stroke volume (SV) (E), cardiac output (CO) (F), ejection time (EJT) (G), total peripheral resistance (TPR) (H), and forearm blood flow (I), measured continuously over 2 hours after drug ingestion, except for forearm blood flow. Forearm blood was measured over a time period of 2 minutes just before the start and in between the stress tests. Dotted line denotes baseline values between the stress tests. Repeated measures 2-way ANOVA; mean ± SEM (*/ + / # P < 0.05, **/ ++ / ## P < 0.01 using Bonferroni’s post-hoc analysis; + and # represent significant change in any parameter over time seen with placebo and CBD, respectively; denotes overall significant difference between 2 treatments).

There was a trend toward reduction in total peripheral resistance (TPR, Figure 1H ) with CBD in the latter half of the resting period, and a significant reduction in forearm skin blood flow before the start of the stress tests ( Figure 1I ; P < 0.01).

Effect of CBD on cardiovascular parameters mental stress.

The individual blood pressure responses of healthy volunteers to the stresses are presented in Figure 2 , showing the average baseline systolic or diastolic blood pressure in the 4 minutes preceeding the stress test, the peak response during stress, and the average recovery response in the 4 minutes after the stress test.

Individual systolic and diastolic blood pressure responses to all stress tests after a single dose (600 mg) of cannabidiol (CBD) or placebo in healthy volunteers (n = 9).

Green color coding shows subjectS who had a reduced (compared with placebo) blood pressure response to stress after taking CBD, and red color coding shows an increased blood pressure response to stress after taking CBD.

Mental stress test.

Cardiovascular response to mental stress after a single dose (600 mg) of cannabidiol (CBD) in healthy volunteers (n = 9).

The effects of placebo (closed square) and CBD (open square) on systolic blood pressure (SBP) (A), diastolic blood pressure (DBP) (B), mean arterial blood pressure (MAP) (C), heart rate (HR) (D), stroke volume (SV) (E), cardiac output (CO) (F), ejection time (EJT) (G), total peripheral resistance (TPR) (H), and forearm blood flow (I), measured continuously just before, during, and after mental arithmetic test (dotted line denotes stress test period), except for forearm blood flow. Measurements for forearm blood flow were made over a 2-minute window just before, during, and after the stress test. Repeated measures 2-way ANOVA; mean ± SEM (+ and # denote significant change in a parameter during the stress period seen with placebo and CBD, respectively). + / # P < 0.05, ++ /# # P < 0.01.

Exercise stress test.

Cardiovascular parameters in response to exercise stress after a single dose (600 mg) of cannabidiol (CBD) in healthy volunteers (n = 9).

The effects of placebo (closed square) and CBD (open square) on systolic blood pressure (SBP) (A), diastolic blood pressure (DBP) (B), mean arterial blood pressure (MAP) (C), heart rate (HR) (D), stroke volume (SV) (E), cardiac output (CO) (F), ejection time (EJT) (G), total peripheral resistance (TPR) (H), and forearm blood flow (I), measured continuously just before, during, and after isometric exercise test (dotted line denotes stress test period), except for forearm blood flow. Measurements for forearm blood flow were made over a 2-minute window just before, during, and after the stress test. Repeated measures 2-way ANOVA; mean ± SEM (*/ + / # P < 0.05; **/ ++ / ## P < 0.01; ***/ ### P < 0.001; ****/ #### P < 0.0001 using Bonferroni post-hoc analysis; + and # denote significant change in a parameter during the stress period seen with placebo and CBD respectively).

Cold stress test.

Cardiovascular response to cold stress after a single dose (600 mg) of cannabidiol (CBD) in healthy volunteers (n = 9).

The effects of placebo (closed square) and CBD (open square) on systolic blood pressure (SBP) (A), diastolic blood pressure (DBP) (B), mean arterial blood pressure (MAP) (C), heart rate (HR) (D), stroke volume (SV) (E), cardiac output (CO) (F), ejection time (EJT) (G), total peripheral resistance (TPR) (H), and forearm blood flow (I), measured continuously just before, during, and after cold pressor test (dotted line denotes stress test period), except for forearm blood flow. Measurements for forearm blood flow were made over a 2-minute window just before, during, and after the stress test. Repeated measures 2-way ANOVA; mean ± SEM (*/ + / # P < 0.05, **/ ++ P < 0.01, ***/ +++ P < 0.001, ****P < 0.0001 using Bonferroni post-hoc analysis; + and # denote significant change in a parameter during the stress period seen with placebo and CBD, respectively).

Looking at the individual response to the cold pressor test, 8 of 9 subjects had a lower SBP during the cold stress and in the recovery period after taking CBD ( Figure 2 ). Six of 9 subjects had a lower DBP during the cold pressor, and 7 of 9 subject had a lower DBP in the recovery period after taking CBD ( Figure 2 ).

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Discussion

Based on preclinical evidence, the aim of this study was to test the hypothesis that CBD would reduce the cardiovascular response to stress in healthy volunteers. We found that resting blood pressure was lower after subjects had taken CBD and that CBD blunted the blood pressure response to stress, particularly in the pre- and poststress periods. Post-hoc analysis showed an overall trend of lower SBP, MAP, DBP, SV, TPR, forearm skin blood flow, and left ventricular EJT and a higher HR in subjects who had taken CBD. These hemodynamic changes should be considered for people taking CBD and suggest that further research is warranted to establish whether CBD has any role in the treatment of cardiovascular disorders.

We have shown for the first time that to our knowledge that, in humans, acute administration of CBD reduces resting blood pressure, with a lower stroke volume and a higher heart rate. This response may be secondary to the known anxiolytic properties of CBD (16) and may account for the lack of anticipatory rise in blood pressure seen with placebo. These findings are in contrast to previous studies in humans, where CBD at the same dose did not affect baseline cardiovascular parameters (17–19), although changes in the cardiovascular system were not the primary outcome of these studies. In the present study, CV parameters were measured continuously, while in previous studies, monitoring for SBP, DBP, and HR were performed manually at only 1, 2, or 3 hours after drug delivery. Additionally, our subjects were cannabis naive, while the subjects of other studies had used cannabis in the past. Since tolerance may develop to the hemodynamic response to CBs in humans, this may explain the differences between studies.

THC, the major psychoactive component of cannabis, is known to cause tachycardia and orthostatic hypotension in humans (20), a hemodynamic response similar to that observed to CBD in the present study. THC is a partial agonist at both CB1 and CB2 receptors (21), and the effects of THC on heart rate are mediated through CB1 receptors (20). CBD does not bind with any great affinity to CB1, but it can interact indirectly by augmenting CB1 receptors’ constitutional activity or endocannabinoid tone, the so called indirect agonism (22). We recently showed that CBD also causes endothelium-dependent vasorelaxation in isolated human mesenteric arteries through CB1 activation (11). Therefore, it is possible that the changes in hemodynamics brought about by CBD are mediated through CB1.

CBD may cause sympathoinhibition (through CB1 or some other mechanism), thereby preventing an increase in blood pressure and cardiac output, causing a compensatory rise in heart rate to maintain cardiac output. Indeed, the changes in SBP preceded any changes in HR. Another possibility is that CBD inhibits cardiac vagal tone, thereby increasing heart rate (despite any potential sympathoinhibition). A recent study in male Sprague-Dawley rats showed that GPR18 activation in the rostral ventrolateral medulla (RVLM) by abnormal CBD (Abn-CBD) resulted in reduced blood pressure and increased heart rate (23) (similar to that observed in the present study). The same study showed that pretreatment with atropine and propranolol fully abrogated the HR response, suggesting a role for the autonomic nervous system. CBD is a weak partial agonist at GPR18 (24).

Effect of CBD on cardiovascular parameters in response to mental stress.

Mental arithmetic has been shown to cause a rise in MAP and muscle sympathetic nerve activity (MSNA) (25) and vasodilatation in forearm skeletal muscle (26). In our study, none of the cardiovascular parameters other than HR, DBP, and SV were affected, suggesting that the level of stress to this test was minimal. This could be because of the added visual stimulus of a computer screen, which would have helped volunteers perform the task. Overall, there was trend for lower SBP, DBP, MAP, SV, TPR, and forearm skin blood flow in subjects who had taken CBD, particularly in the pre– and post–stress test periods. Like resting cardiovascular parameters, these changes may indicate anxiolytic effects of CBD and/or generalized sympathoinhibition.

Effect of CBD on cardiovascular parameters in response to exercise stress.

Isometric exercise produces a pressor response, via sympathoexcitation, originating in the contracting muscle and relayed to the RVLM via the nucleus of solitary tract. The end result is a rise in heart rate and cardiac output and vasoconstriction in nonexercising organs (27–29). There is increased skeletal muscle blood flow in the nonexercising limb, which is sensitive to atropine and propranolol (30). A similar response was seen in our study, where isometric exercise caused a significant rise in SBP, DBP, MAP, and HR and an increase in forearm blood flow, although this was significant in the placebo group only. Subjects who had taken CBD had reduced blood pressure during the exercise stress test, and this was most pronounced in the pre- and posttest period. Before the exercise stress, HR was higher and SV lower in volunteers when they had taken CBD, and this trend continued throughout exercise stress and in the poststress period. There was also a significant reduction in EJT with CBD, which represents a reciprocal change to increased HR. The rise in cutaneous blood flow was only seen with placebo and not with CBD, possibly suggesting reduced β2 adrenergic–mediated vasodilatation, which could be a result of general sympathoinhibition or a specific effect at the β2 adrenoceptors. The tissue distribution of β2 adrenoceptors and CB1 receptors overlaps in many tissues, including in the cardiovascular system (31). At the cellular level, a complex physical and functional interaction between these 2 receptors has been demonstrated; there is evidence of cointernalization of β2 adrenoceptors with CB1 receptors, leading to desensitisation of β2 adrenoceptors (31).

Effect of CBD on cardiovascular parameters in response to cold stress.

Cold stress causes intense sympathoexcitation, producing a tachycardic and pressor response, and an increase in MSNA (32, 33). The pressor response is due to an initial rise in CO, in response to increased HR and a later increase in MSNA, causing vasoconstriction. Both MAP and TPR show a linear correlation with MSNA during cold stress (34). In our study, cold stress produced a pressor response in both groups, but, interestingly, while SBP and MAP continued to rise with placebo throughout the test period, the pressor response to cold was blunted in subjects who had taken CBD, and SBP and MAP were significantly lower. In keeping with this, TPR was lower with CBD than placebo, suggesting a possible inhibition of sympathetic outflow. This could also be due to analgesic properties of CBD (35), reducing cold stress and therefore minimizing the sympathetic response (also explaining why the cold pressor test was affected more by CBD than the exercise test). In the animal study of Resstel and colleagues (13), the authors suggested that the modulation of cardiovascular response was most likely secondary to attenuation of emotional response to stress. However, given our findings that CBD produced similar changes in cardiovascular parameters — though to a variable degree — during rest and stress, this may indicate that CBD also has direct cardiovascular effects.

Safety and tolerance.

CBD was well tolerated, and there were no adverse events on the day of stress tests. None of the subjects reported any adverse events over the following week.

Conclusion.

Our data show that a single dose of CBD reduces resting blood pressure and the blood pressure response to stress, particularly cold stress, and especially in the post-test periods. This may reflect the anxiolytic and analgesic effects of CBD, as well as any potential direct cardiovascular effects. CBD also affected cardiac parameters but without affecting cardiac output. Giving the increasing use of CBD as a medicinal product, these hemodynamic changes should be considered for people taking CBD. Further research is also required to establish whether CBD has any role in the treatment of cardiovascular disorders such as a hypertension.

Methods

Study design.

The study was a randomized, crossover design with each subject given CBD (BN: K12067A) or placebo (both gifts from GW Pharmaceuticals) in a capsule in a double-blind fashion, with a minimum time interval of at least 48 hours (range 3–16 days), taking place at the Division of Medical Sciences, School of Medicine, Royal Derby Hospital. Allocation was decided by a coin toss, and block randomization was employed by S.E. O’Sullivan, who assigned participants. K.A. Jadoon carried out all study visits, and data analysis was blinded.

During an initial visit, subjects were familiarized with the stress tests and with noninvasive cardiovascular (CVS) monitoring, and an electrocardiogram (ECG) was done to rule out any preexisting cardiac conditions. Subjects were advised to fast overnight, to avoid beverages containing caffeine or alcohol, and to avoid strenuous exercise for 24 hours before each of the 2 study visits. Two hours after CBD/placebo was administered, subjects performed various stress tests (36). Noninvasive cardiovascular monitoring using Finometer and laser Doppler flowmetry was carried out during the 2 hours to assess changes in baseline parameters and during the stress test periods.

Visit days.

Upon arrival, subjects were rested for 10–15 minutes, and their baseline blood pressure and heart rate were recorded using a digital blood pressure (BP) monitor. Participants were given a standardized breakfast, and 15 minutes later, they were given either oral CBD (600 mg) or placebo in a double-blind fashion. This is a dose known to cause anxiolytic effects in humans and is comparable with what is used clinically (19, 37–39). Study medication consisted of capsules containing either 100 mg of CBD or excipients, which were a gift from GW Pharmaceuticals. There was no difference between the 2 formulations in color, taste, or smell.

Two hours afterward, subjects were asked to perform the stress tests (36). Timing of the tests was chosen to coincide with peak plasma levels for CBD (18). All the experiments were performed in a sitting position under ambient temperature conditions. Maximum voluntary contraction for the isometric hand grip test was assessed for each subject prior to administering study medication.

After administration of CBD or placebo, subjects remained seated, either doing nothing, reading, or using a computer. During this time, subjects were connected to a calibrated Finometer (Finapres Medical Systems), which uses a finger-clamp method to detect beat-to-beat changes in digital arterial diameter using an infrared photoplethysmograph (40). The Finometer gives a continuous signal of beat-to-beat changes in blood pressure and blood flow, and it uses this signal to derive other parameters, including systolic, diastolic, and mean blood pressure; interbeat interval; heart rate and left ventricular ejection time; stroke volume; cardiac output; and systemic peripheral resistance. Baseline cardiovascular data was recorded for 2 hours following administration of CBD or placebo. Forearm blood flow was measured using a calibrated laser Doppler flowmeter (Perimed) (41). For each recording, 5 images of microcirculation were taken, over an area 19 mm × 19 mm, using the upper third of the left forearm under high resolution. After 2 hours, subjects underwent the cardiovascular stress tests in the following order: mental arithmetic, isometric exercise, and cold pressor test.

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The mental arithmetic test consisted of calculating a sum every 2 second for 2 minutes. Subjects were seated in front of a computer screen, and a PowerPoint presentation delivered a slide with a simple mathematical sum of a 3-digit number minus a smaller number (e.g., 317 – 9, 212 – 11, 185 – 7) every 2 seconds; the subject had to give the answer verbally. In the isometric exercise stress test, using a dynamometer, handgrip was maintained at 30% of maximum voluntary contraction (MVC) for 2 min. For the cold pressor test, subjects immersed their left foot (up to ankle) in ice slush (temperature 4°C–6°C) for 2 minutes. Cardiovascular parameters were measured continuously using the Finometer, while skin blood flow measurements were taken just before, during, and 5 minutes after each test. Each stress test lasted for 2 minutes, and there was a recovery period of at least 10 minutes.

Statistics.

Data were analyzed using repeated measures ANOVA to determine the effect of treatment and time on different variables using GraphPad PRISM version 6.02. Level of significance was set at α = 0.05 and values presented as mean ± SEM. Sidak’s post-hoc test was used to see treatment affect at various time points. Data were not unblinded until after statistical analysis.

Study approval.

Ten healthy young male volunteers, mean age 24 years (range 19–29), with no underlying cardiovascular or metabolic disorders, were recruited for this study, which was approved by the University of Nottingham Faculty of Medicine Ethics Committee (study reference E18102012). Written informed consent was obtained according to the Declaration of Helsinki. Exclusion criteria included any significant cardiovascular or metabolic disorder or use of any medication. All the volunteers were nonsmokers and had taken no prescribed or over-the-counter medication within a week prior to randomization. No volunteers had ever used cannabis.

Author contributions

KAJ helped with study design, researched data, wrote the manuscript, and reviewed/edited the manuscript. GDT reviewed/edited the manuscript. SEO was involved in study design and reviewed/edited the manuscript.

Supplementary Material

Acknowledgments

GT is supported by the NIHR Oxford Biomedical Research Centre Programme. The views expressed are those of the author and not necessarily those of the NHS, the NIHR, or the Department of Health.

Footnotes

Conflict of interest: GW Pharma supplied the cannabidiol (CBD) and placebo but did not fund the study.

Reference information:JCI Insight. 2017;2(11):e93760. https://doi.org/10.1172/jci.insight.93760.

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CBD: What is it, and can it help the heart?

CBD is the latest health craze to sweep the high street, with claims it can help everything from chronic pain and inflammation to anxiety. But what is CBD, and can it really help the heart? Emily Ray finds out.

What is CBD, and is it legal in the UK?

CBD, or cannabidiol, is a chemical that’s extracted from the leaves and flowers of the cannabis plant. Cannabis itself is an illegal class B drug, as is the compound THC (tetrahydrocannabinol) which it contains. But pure CBD isn’t illegal, as it doesn’t cause the intoxicating effects of cannabis.

What CBD products are available?

The choice of CBD products has exploded recently: you can buy oils, capsules, muscle gels, sprays and oral drops, as well as beer, tea, sweets, hummus and even CBD-infused clothing.

Many of these can be easily picked up from reputable high street stores, such as Holland & Barrett or Boots.

Prices can be high: a 500mg bottle of CBD oil oral drops could set you back as much as £45. Not that this has put people off: over the past two years, sales of CBD have almost doubled in the UK, putting regular users at an estimated quarter of a million.

What is CBD used for?

A 2018 report by the World Health Organization suggested that CBD may help treat symptoms relating to conditions such as cancer, Parkinson’s disease, multiple sclerosis (MS), anxiety, depression, insomnia and Alzheimer’s disease.

However, it also notes that this research is still in the early stages, and that more studies are needed before conclusions can be drawn on whether CBD is effective.

CBD’s popularity has been given a boost by the fact that two CBD-containing medicines have been approved for prescription use by the NHS in England: Epidyolex, which has been found to reduce the number of seizures in children with severe epilepsy, and Sativex, which contains a mixture of CBD and THC, and is licensed for treatment of muscle stiffness and spasms in people with MS.

Does CBD work?

Harry Sumnall, Professor in Substance Use at Liverpool John Moores University, says: “In terms of the products found in shops, there’s virtually no evidence to support the claims made for a lot of them. There’s a lot of marketing that says CBD is a ‘miracle of the modern age’; however, the marketing has actually overtaken the evidence of what it’s effective for.”

“In terms of the products found in shops, there’s virtually no evidence to support the claims made for a lot of them.”

Harry Sumnall, Professor in Substance Use at Liverpool John Moores University

Professor Sumnall argues that while it could be effective for some people, in some of these cases the results could be caused by the placebo effect (where the patient’s belief in a treatment makes them feel better). The placebo effect can be powerful, but Professor Sumnall warns that if people try CBD oil instead of speaking to their doctor, it could cause a problem.

The biggest difference between CBD used in clinical trials and in stores is the dose. Research has shown that some products contain very little CBD (or even none at all). Others contain THC or other illegal drugs, or even alcohol instead of CBD. By contrast, in clinical trials the CBD is purified, manufactured to a very high standard and given at a much higher dose. It is also taken regularly and under medical supervision.

Since 2016, any CBD product that is presented as having medicinal value must be licensed and regulated as a medicine, regardless of whether it is actually effective. Manufacturers must follow very specific and robust rules around production, packaging and the information provided.

But so far, Professor Sumnall points out, CBD products in shops are marketed as food supplements, not medicines, so none of them have gone through this process.

Can CBD help the heart?

Inflammation is part of the process that leads to many diseases, including coronary heart disease, high blood pressure and stroke, and there is some evidence that CBD has anti-inflammatory properties. Other studies have suggested that CBD can have a protective effect on the heart: this has been proven in rats after a heart attack and in mice with some of the heart damage associated with diabetes. But because these studies are often based on findings in a lab or in animals, not in humans, we cannot yet be confident that CBD will benefit the human heart.

There is ongoing research into the use of purer forms of CBD for a variety of conditions, including heart and circulatory diseases and, in particular, diseases of the heart muscle, including myocarditis and some types of cardiomyopathy.

Some of this work is still in animals, and much more research is needed before we can definitively say that CBD can help in this area.

“It’s clear that CBD has potential,” says Professor Sumnall, “but we’re at a very early stage of that research.”

  • Always talk to your doctor if you’re thinking about taking a CBD product to supplement your existing treatment.

Meet the expert

Harry Sumnall is a Professor in Substance Use at the Public Health Institute, Liverpool John Moores University. He was a member of the UK Government’s Advisory Council on the Misuse of Drugs between 2011 and 2019.

Marijuana and heart health: What you need to know

Access to marijuana is growing, but marijuana benefits and its risks have not been carefully studied.

In many states in this country, you can legally use marijuana. Smoking is the fastest way to feel the effects of marijuana, which is derived from the Cannabis sativa plant. Yet marijuana smoke contains many of the same toxins, irritants, and carcinogens found in cigarette smoke — a known contributor to heart disease as well as cancer.

Marijuana cultivation and use dates back some 6,000 years. However, the cardiovascular and other health effects of cannabis aren’t well studied. That’s partly because under federal law, cannabis is a Schedule I substance, meaning it has “no currently accepted medical use and a high potential for abuse.” That designation places numerous restrictions on researchers, making it difficult to carry out rigorous research on marijuana.

As a result, everything we’re told about what marijuana does or doesn’t do should be viewed with a certain amount of caution. This holds equally true for the risks as well as the benefits.

Pot and pain

Some of the evidence supporting the medical use of marijuana is marijuana’s benefits for managing chronic pain. Cannabinoid compounds (see “Cannabis 101”) interact with receptors in nerve cells to slow down pain impulses and ease discomfort. Cannabinoids also have been shown to be effective in quelling nausea and vomiting. In addition, marijuana is a powerful appetite inducer. The combination of these attributes makes marijuana a therapeutic option for people coping with the side effects of chemotherapy and others who have unintended weight loss. However, in conditions where gaining extra weight might exacerbate existing health problems, such as diabetes, appetite stimulation would be counterproductive.

Cardiovascular effects

One of the few things scientists know for sure about marijuana and cardiovascular health is that people with established heart disease who are under stress develop chest pain more quickly if they have been smoking marijuana than they would have otherwise. This is because of complex effects cannabinoids have on the cardiovascular system, including raising resting heart rate, dilating blood vessels, and making the heart pump harder. Research suggests that the risk of heart attack is several times higher in the hour after smoking marijuana than it would be normally.

While this does not pose a significant threat to people who have minimal cardiovascular risk, it should be a red flag for anyone with a history of heart disease. Although the evidence is weaker, there are also links to a higher risk of atrial fibrillation or ischemic stroke immediately following marijuana use. Consistent with these links, studies also suggest that marijuana smoking may increase the long-term death rate among heart attack survivors.

Questions remain on marijuana’s benefits and risks

Most of the evidence linking marijuana to heart attack and stroke is based on reports from people who smoked it. So, it’s hard to separate the effects of cannabinoid compounds on the cardiovascular system from the hazards posed by the irritants and carcinogens contained in the smoke. Because cannabis smoke is known to cause airway inflammation, wheezing, and chest tightness, people with lung diseases should not smoke it. People with mental health disorders or at risk of addiction should carefully consider the potential harms prior to using marijuana.

Cannabis 101

The cannabis plant contains more than 100 unique chemical components classified as cannabinoids. These are the active ingredients that bind to specific receptors in the brain and other parts of the body. The two most prevalent types are tetrahydrocannabinol (THC), which is primarily responsible for the mind-altering properties sought out by recreational users, and cannabidiol (CBD), which has no psychoactive effect.

The magnitude of marijuana’s psychoactive effect depends on the THC level in the particular strain of plant, which parts of the plant are used, and the route through which the drug enters the body. Legalization in many states has led to the breeding of strains that are three to seven times more potent than those available three decades ago.

The impact of smoked or inhaled marijuana is generally felt within a few minutes and lasts two to four hours. Marijuana ingested in food or beverages kicks in more slowly and lasts longer.

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