Is Cannabis the Best Treatment for Epilepsy?

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There are many ways of dividing humanity into two. One such way is to separate those who desire that everything should be explicable, preferably by a single grand overarching theory, and those who desire that a mystery should always remain. I suspect that believers in alternative medicine are predominantly of the latter disposition. They probably also derive a certain pleasure from defying and sometimes even triumphing over medical or other authority.

If I am right, extravagant belief in the therapeutic benefits of cannabis should decline as its claims are investigated with scientific rigour. If a chemical found in cannabis is prescribed in precisely the same manner as, say, antihypertensives, it will lose the mystique of its derivation. Like most drugs, it will merely be useful in some cases.

There’s an interesting review in the New England Journal of Medicine on the use of cannabis-derived substances in cases of epilepsy. Although new anticonvulsants have been developed in recent years, the proportion of epilepsy that remains untreatable has stayed more or less the same at 30 percent. The article contained an admirably clear exposition of the theoretical reasons why various chemicals found in cannabis (more than 500!) might work in cases of epilepsy.

The human brain has naturally occurring cannabinoid receptors, and there’s evidence of their disruption in some forms of epilepsy. Work in animals suggests that substances that block cannabinoid receptors lower the seizure threshold, which is a contributing factor for epilepsy. An epidemiological study conducted in New York has found that adults who smoked cannabis within the last 90 days were less likely to have an epileptic seizure than those who did not.

Anecdotal evidence dating from a surprisingly long way back also suggests a therapeutic effect of cannabis on the rate and severity of epileptic fits.

But none of the above proves the case for cannabis as a treatment for epilepsy. The history of therapeutics is littered with treatments that did not work in the end but were initially supported by exactly the same kind of evidence in their favor.

Few properly controlled trials have been performed: two were positive and two were negative. Among the difficulties of investigating the matter scientifically are the sheer number of chemical compounds to be tested, and also regulatory prohibitions. It’s important to remember that not all the substances found in cannabis have the kind of psychological effects that make it popular with aficionados.

Properly conducted double-blind trials are necessary because the placebo effect is strong, particularly in children. The authors sum up very succinctly the pitfalls of all other kinds of evidence adduced by enthusiasts (not only for cannabis, but for all treatment both orthodox and, especially, unorthodox):

The gap between patient beliefs and available scientific evidence highlights a set of factors that confound cannabinoid research and therapy, including the naturalistic fallacy (the belief that nature’s products are safe), the conversion of anecdotes and strong beliefs into facts, failure to appreciate the difference between research and treatment, and a desire to control one’s care, including access to therapies of perceived benefit.

Intriguingly, the authors quote one study that showed that parents of epileptic children who moved to Colorado so that their children could receive cannabinoid treatments reported more than twice as much benefit as the parents who already resided in the state (47 percent compared to 22). By itself, this does not prove very much, unless the children of the two groups were similarly afflicted in the first case – epilepsy not being a single condition with an identical degree of severity. Nevertheless, it is what I would have expected.

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