So, Let’s Take A Look at This New Study That Says Recreational Cannabis Use Increases Stroke Risk
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 has recently been reported at the Montreal Stroke Congress. The discussed study looked at 2.3 million hospitalized individuals who smoked cannabis recreationally and concluded that 1.4% of them developed stroke during that time frame. They also reported that the incidence of stroke increased from 1.3% to 1.5% during the four years, while the stroke prevalence nationwide remained constant. This 0.2% increase amounts to 64 patients over the four years.
Whether or not this is a significant increase that prove causality is uncertain at this time. After all, multiple preclinical studies have shown that cannabinoids in fact provide protective effect when it comes to 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 that the part of the brain cell called mitochondria, which are responsible for cellular energy metabolism, were affected in a THC dose-dependent manner. Production of hydrogen peroxide, which may lead to oxidative stress was markedly increased, and generation of reactive oxygen species such as hydrogen peroxide has been associate with stroke in humans.
This was achieved by exposing isolated mitochondria to 30 millimolar concentrations of THC, which arguably is very high and it is more likely than not that mitochondria in human cells do get exposed to such concentrations, even the authors acknowledged. Therefore, only abnormally large doses of THC have been linked to increased oxidative stress 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.
Impedance of blood flow in the brain leads to depletion of oxygen in the local brain tissue, a condition referred to as ischemic stroke. This reduction of blood flow may occur in situations when blood vessels become constricted, termed vasoconstriction. The hypothesis that cannabinoids act as vasoconstrictors leading to stroke has not been confirmed.
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 is pointing towards anti-oxidant, anti-inflammatory and anti-vasoconstrictive effects of cannabinoids in the brain, all of which are predicted to 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 is not really translatable to cannabis use because of the presence of other phytocannabinoids and other molecules such as terpenes. Many of them have been found to have anti-inflammatory and anti-oxidant properties, and thus are expected to act in synergy in protecting the brain against strokes.