hypertension Cannabis has been shown to have some effect on the symptoms of hypertension, but as with many diseases, the link has not been fully determined and much controversy remains. Hypertension is a chronic condition which increases the arterial blood pressure, forcing the heart to work harder than usual and often putting it under enormous strain. Hypertension is also associated with an increased risk of atherosclerosis, stroke, aortic aneurysm and peripheral arterial disease, and is the most significant preventable risk factor for premature death throughout the world.
Prevalence of hypertension in the USA
The prevalence of the condition is increasing in many economically developed regions of the world, as diets become richer in fat and processed carbohydrates, and lifestyles grow generally more sedentary. In the USA, the prevalence of hypertension increased from 29% of adults in 1995 to 34% in 2005, but as awareness and prevention techniques have greatly improved in recent years, prevalence may now be dropping slightly. In 2007-2008, the CDC estimated a 29.7% prevalence, which fell slightly to 28.6% in 2009-2010.
Cannabis has been shown to have some effect on the symptoms of hypertension, but as with many diseases, the link has not been fully determined and much controversy remains. Several cases of heavy cannabis users who have developed hypertension and various related complications after long-term use have been documented, such as a 56-year-old man who presented symptoms of severe shortness of breath, osteoporosis, occipital stroke and an increased vascular age of 69.8 years.
Is there a risk distinct from that caused by smoking tobacco?
Another case involved a 23-year-old male who experienced hypertension and acute coronary syndrome after several years of cannabis use. A 35-year-old Afro-Caribbean woman who had smoked cannabis infrequently in the past, but had not consumed any within the year prior to seeking treatment, also presented with severe symptoms of hypertension. However, as all these cases involved individuals who regularly smoked tobacco, it is unreasonable to suggest that cannabis was the primary risk factor.
While heavy, prolonged use of smoked cannabis may present an increased risk of hypertension, there is little evidence to support this theory, and in smaller doses use of the drug may in fact benefit sufferers. There is abundant evidence of the vasodilatory effect of cannabis; indeed, the reddening of the conjunctiva of the eye observed in many cannabis users is a visual indication of this phenomenon. Acute THC intoxication causes dilation of the peripheral blood vessels and orthostatic (or postural) hypotension, a sudden drop in blood pressure that occurs when standing up or stretching.
The hypotensive effect of THC
A study into the hypotensive effect of THC on cats concluded that intravenous administration of 2mg/kg led to “marked decreases in blood pressure and heart rate which developed gradually and were of prolonged duration”. However, the fact that THC has been shown to cause tachycardia (increased heart rate) in humans suggests that different mechanisms are affected and further human-based studies are still needed.
For hypertensives, any agent that increases the heart rate, thereby putting greater strain on an already-overworked organ, is usually a highly inappropriate choice. However, although some suggest that this implies an increased risk for hypertensives, some believe that the hypotensive effect of THC outweighs the potential harm of subsequent reflex tachycardia. More research must be undertaken to fully clarify this controversy.
The vasodilatory effect of THC and anandamide
THC’s endogenous analogue anandamide is also known to exert a powerful vasodilatory effect, and its action on the peripheral CB1-receptors is accompanied by an increase in another vasodilator, calcitonin-gene-related peptide. Further, the actions of anandamide may be mediated by other endocannabinoids in as yet unknown ways.
It is clear from past research that the actions of cannabinoids such as THC are mediated by other substances in various ways. A 2006 study into the effects of THC on hypotension determined that while activation of the CB1-receptor by THC had an inconsistent effect on blood pressure, administering the selective CB1 receptor antagonist rimonabant together with THC produced more pronounced hypotensive effects, in a greater percentage of patients.
Cannabigerol and vasodilation
THC is also not the only phytocannabinoid that has an effect on blood pressure. Research conducted in 2006 at the Hebrew University School of Pharmacy concluded that a synthetic form of cannabigerol (CBG) was effective in reducing blood pressure and causing vasodilation in rats. With further research, it is likely that other cannabinoids will reveal their own specific effect on vasodilation and hypertension.
As well as further clarification of the complex relationships between blood pressure, cardiovascular health and the function of the endocannabinoid system, more investigation into the comparative risks and benefits of smoking compared to other forms of consumption must be undertaken. The staggeringly high prevalence of hypertension throughout the world renders the need for such research extremely high, and cannabis’ status as a risk factor or a valid treatment option must be determined beyond question.
Cannabis’ efficacy must be rigorously examined
The effect of smoked cannabis on hypertension and cardiovascular health is not clear, and may prove to represent a slight increased risk factor. There is evidence indicating that cannabis administered in small to moderate doses can reduce hypertension and even lead to mild hypotension; however, the risk of tachycardia may outweigh the benefit for some patients.
For individuals suffering from hypertension, alternative methods than smoking are advisable. Consultation with a medical advisor is of the utmost importance, due to the severity of the condition and the high risk of extreme, potentially fatal complications that typically arise from it. Careful experimentation to find the most appropriate dosage and method of consumption is advisable; vaporising, sublingual application, oral consumption, or use of THC capsules always represent a safer and healthier choice.