Study reveals disturbing effects of cannabis on the brain, adding caution to legalisation debate

Sam Woolfe

New research shows that cannabis users have lower blood flow to the brain compared to non-users. Scientists were also able to pinpoint one brain area that has the lowest blood flow in cannabis users. This is the hippocampus.

A risk to brain function

The hippocampus plays a key role in memory and learning. And it is one of the areas affected by Alzheimer’s. The researchers say that low blood flow in the hippocampus suggests a higher vulnerability to Alzheimer’s.

Dr George Perry, editor in chief of the Journal of Alzheimer’s Disease, said troubling effects on the hippocampus “may be the harbingers of brain damage”. Meanwhile, study lead author Daniel Amen underscores that “marijuana can have significant negative effects on brain function”.

He continues:

The media has given the general impression that marijuana is a safe recreational drug, this research directly challenges that notion. In another new study just released, researchers showed that marijuana use tripled the risk of psychosis. Caution is clearly in order.

Caution is in order. Especially since country-wide legalisation of cannabis in the US is on the horizon. Risking damage to brain function is serious. And making yourself more prone to Alzheimer’s is a cause for concern. But what the research doesn’t highlight is the kind of cannabis that the participants were using.

Is the problem high-strength cannabis?

Daniel Amen was referring to this study, suggesting that cannabis abuse can triple the risk of psychosis. Despite the difficulty in determining causality, let’s assume that the risk is real. Similar research – again, prone to issues of confusing correlation with causation – says the risk comes from smoking high-strength cannabis (aka ‘skunk’) every day.

Skunk is a generic term for strains of cannabis that contain high levels of THC – the compound that gets you high. THC can also induce the symptoms of psychosis in healthy people and worsen symptoms in people already experiencing them.

CBD – another compound in the plant – negates these symptoms. It has anti-psychotic effects. The problem with skunk is that it contains high levels of THC and low levels of CBD. Hash, on the other hand, contains about equal levels of both. In this way, skunk and hash carry completely different safety profiles.

The report’s warning about the risk of cannabis might have more to do with potency than the drug itself. For example, other research has linked heavy cannabis use to impaired learning, memory and intelligence. But given that skunk dominates the black market, the real problem could be the ratio of THC to CBD.

This new study does not imply that legalisation is now riskier. After all, rates of teen cannabis use in Colorado actually dropped following legalisation. This is perhaps due to the fact that, as the dealers disappeared, teens were then unable to buy the drug from licenced, age-restricted shops.

How cannabis is regulated is important. The Drug Policy Alliance argues that in a regulated market, customer safety should be promoted. This would include informing customers about levels of THC and CBD in particular strains. In this way, users can make safer choices.

More research needed

Another useful study could involve comparing the brains of heavy skunk and hash users, moderate users of both, and a control group. We might not see such a high risk of brain damage in hash users.

In any case, the reason why it’s so difficult to study cannabis is because it’s a controlled Schedule I drug. Professor David Nutt has also written about how drug laws impede important medical research.

There are fears about legalisation leading to a spike in use. And we shouldn’t take this risk lightly. If potent cannabis becomes commercially available, we could see a higher incidence of psychosis. But as decriminalisation in Portugal demonstrates, fears of increased use seem not to have materialised. In fact – like with Colorado – drug use among teenagers and young people decreased.

This recent research on cannabis and brain damage raises many questions. The findings may only hold true for skunk, but not hash or less potent strains of cannabis. Further research is clearly needed.

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Featured image via Wikimedia

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