'All medicines are drugs, not all drugs are medicines'
Annabel Travers | 27 March 2017

We’re taught when we’re young: ‘all medicines are drugs, but not all drugs are medicines’. So if I told you that a glass of red wine a day will make you live longer and lower cholesterol, what would you think? But alcohol is a legal drug. If I told you that cannabis had a multitude of medicinal benefits, what would you say?

 

The current status of Cannabis in the UK is a class B drug, and under federal law in the states it’s a schedule 1 drug. In both cases, cannabis possession is not permitted under any circumstances. And yet, individual state legislation in 18 North American states has legalized small amounts of cannabis possession for medical purposes. What’s more, the recent election saw Colorado and Washington becoming the first states to allow a small amount of cannabis for recreational use - under strict regulation and guidelines of course.

 

It seems strange that such a drug, which has a reputation for high addiction and crime rates, is being put through this social transformation; one that sees this psychoactive drug as a medicine. Once I’ve explained the science behind the claims it might not be so surprising.

 

The most important, fundamental thing to understand is the physiology of the cannabis plant. Cannabinoids are the active components of cannabis and are found in the leaves and flowers of the plant. ∆9-tetrahydrocannabinol (THC) is the most abundant, and is responsible for the psychotropic effects experienced when cannabis is ingested or inhaled. Cannabidiol (CBD) is the second most abundant, and is non-psychoactive. CBD can dampen the psychoactive effects of THC to effectively reduce the potency of THC, which is why strains of cannabis bred for elevated potency are selectively produced to have a high THC: CBD ratio.

 

The human body has its own endogenous cannabinoids, also known as endocannabinoids. The two main endocannabinoids are anandamide and 2-arachydonoylglycerol. These are retrograde neurotransmitters, meaning they travel backwards across a synapse (the point at which signals travels between nerves in the central nervous system) from the postsynaptic neuron, to the presynaptic neuron. At the presynaptic neuron, the cannabinoids bind to receptors called CB1 type receptors. They also bind to receptors from other pathways such as the serotonin receptors (5-HT3) and the vanilloid receptors (VR1). They do this either antagonistically or agonistically, depending on the affinity between the cannabinoid and the receptor. Agonistic binding triggers a response by the cell, whereas antagonistic binding will suppress or block the response caused by the agonist. Retrograde signaling of the CB1 receptor acts like a dimmer switch, and modifies the neurotransmitter chemicals being released from the postsynaptic neuron, which then adjusts the composition of neurotransmitters being released by the presynaptic nerve. Transporter chemicals can remove the cannabinoid from the synaptic space and take them to other parts of the body.

 

CB1 receptors are found in the central nervous system, whereas CB2 receptors are found on immune cells such as macrophages, natural-killer cells and T-cells.  Exogenous cannabinoids derived from the cannabis plant mimic these endogenous cannabinoids.

 

That’s the basic science. The implications of this are varied. Primarily research is being done into how it will help chemotherapy. A big side-effect to chemotherapy is nausea and vomiting – this is called Emesis. Cannabinoids have anti-emetic effects. Trials have suggested that cannabinoids are more effective at treating nausea than many of the existing anti-emetic drugs (dopamine receptor antagonists).

 

This is excellent news for those undergoing chemotherapy. But, of course, there are concerns – we are still dealing with a drug not just a synthetic medicine.

 

Worries arise, quite rightly, about cannabis causing depression. I am not naïve and have seen the studies; there is a correlation between frequent cannabis use and depression. But, it must be emphasized that this is only a correlation, and this does not prove a causal effect. The trend suggests that an onset of depression is at an increased risk for those who begin smoking at a younger age, suggesting that cannabinoids are unhealthy for the developing brain. Furthermore, there are three strong arguments that suggest why this correlation occurs without being causal: self-medication; socio-economic factors; artifact. Self–medication is when people smoke cannabis to treat pre-existing depressive symptoms. The factors refer to those circumstances, such as deprived upbringing, that led the individual to be depressed and smoke cannabis in the first place. The artifact implies the link does not exist. In other words, cannabis cannot be certified to cause depression.

 

As well as the concerns about depression cannabis has a reputation as a cause of antisocial and withdrawal behavior. I would point out that it generally appears milder with cannabis than opiates, and the patterns are inconsistent. Symptoms such as restlessness, irritability, agitation, insomnia and nausea are common for short-lived periods of time, although heavy chronic use of cannabis may result in symptoms such as aggression and anger.

 

The current situation concerning modern pharmaceuticals stands thus: there are a number of drugs which exist today, using synthetic or extracted cannabinoids. These include Marinol, a drug designed to aid weight gain in AIDS sufferers using synthetic THC in seasame oil, and Nabilone, another synthetic THC drug used to control emesis in cancer patients. Both are taken orally, and therefore the 9∆THC may metabolise in the liver to form 11∆THC, a more potent form, resulting in increased side effects such as euphoria and anxiety.

 

Cannabis is an illegal and dangerous drug, I am not denying that nor am I encouraging you to start smoking it (illegally). But it cannot be denied either that it has medicinal uses with only small, if often exaggerated, side effects. This article isn’t a comment on whether the UK should fully legalise the use of cannabis but hopefully you can understand that there is more to cannabis than a rebellious high.

James Routledge 2016