Taking A Look At Stroke Risk And Recreational Cannabis
Multiple studies have shown that cannabis helps prevent and repair stroke, so what is this new report that patients are at risk for stroke during recreational cannabis use?
A potential link between cannabis and stroke susceptibility recently came from the Montreal Stroke Congress. The discussed study looks at 2.3 million hospitalized individuals who regularly smoke recreational cannabis. The study concludes that 1.4% of them stroked during that time frame. They also report that the incidence of stroke increases from 1.3% to 1.5% during four years of the study. The stroke prevalence nationwide remained constant. This 0.2% increase amounts to 64 patients over the four years.
Uncertain At This Time
Whether or not this is a significant enough increase to prove causality is uncertain. After all, multiple preclinical studies show that cannabinoids in fact provide protective effects for blood flow to the brain.
To date there are no studies confirming the positive association between cannabis use and neurocardiovascular events. Some authors suggested that there may be a genetic predisposition to the neurovascular toxicity induced by synthetic cannabinoids. Others argue that the toxicity of cannabis related to stroke may be dose-dependent. Toxic effect has been found in rats in vitro using high doses of THC that aren’t necessarily achieved with cannabis.
Researchers found a dose of THC affects the mitochondria, which regulate cellular energy metabolism. Production of hydrogen peroxide saw a major increase, which may lead to oxidative stress. Generation of reactive oxygen species such as hydrogen peroxide associates with strokes in testing.
The scientists achieved this by exposing isolated mitochondria to 30 millimolar concentrations of THC. This a very high concentration. It is more likely than not that mitochondria in human cells do not regularly see exposure to such concentrations. Thankfully, even the study authors acknowledge this fact. Therefore, only abnormally large doses of THC have been link to oxidative stress increases in rats.
In fact, endocannabinoid 2-aracidonylglycerol (2-AG) that activates CB1 in the same manner as THC has been found to reduce the burden of oxidative stress after injury arguing for the protective role of cannabinoid signaling. Thus, this may just be a dose thing.
The Evidence So Far
Impeding blood flow in the brain depletes oxygen in brain tissue. Scientists call this condition “ischemic stroke.” This reduction of blood flow may occur in situations when blood vessels constrict, known as vasoconstriction. We can’t yet confirm the hypothesis that cannabinoids act as vasoconstrictors and lead to stroke.
On the contrary, studies have shown repeatedly that 2-AG acts as a vasorelaxer, which is the opposite process to vasoconstriction. The endocannabinoid system becomes activated after injury in the brain, likely as a protective mechanism aimed at bringing oxygen and nutrients to the site of injury. Therefore, the action of cannabinoids likely leads to vasorelaxation rather than vasoconstriction, which would protect against ischemic stroke.
The scientific evidence points towards anti-oxidant, anti-inflammatory, and anti-vasoconstrictive, effects of cannabinoids on the brain. All of these protect against stroke.
As one study in rats concluded, the negative effects of cannabinoids occur at large doses of THC. However, the study did not address whether concomitant administration of CBD (as occurs in cannabis) counters this effect, as has been shown before. It also did not address that the average consumer would not be able to achieve these high levels of THC!
Furthermore, the effects of THC in isolation are not translatable to cannabis use. This is because of the presence of other phytocannabinoids and molecules such as terpenes. Many of them have anti-inflammatory and anti-oxidant properties. Thus they act in synergy protecting the brain against stroke.