Some new research by Dr Zerrin Atakan and  Prof Philip McGuire has thrown some light on the way cannabis actually works by looking at the effects of THC and CBD – the two principal components of cannabis.

The fact that there are two major active components in cannabis means there’s a big problem for anyone trying to quantify it, which has meant the whole debate has been seriously misrepresented and therefore misunderstood for years.

For just about all other drugs of intoxication (or enlightenment depending on how you look at these things)  there’s really only one consideration: How much of the drug you take, ie the dose. Strong drugs simply give you more of the drug per gram, pint or whatever unit the drug is measured in. In other words, drugs generally consist of an active compound contained within a larger volume of something else which can be considered neutral.

Hence we have a very simple variable to talk about which we call “strength”. Even if they don’t really understand how it works, most people are familiar enough with this concept as it applies to booze and understand that a beer with a 3% ABV is a lot weaker than a beer with 10% ABV, even if they don’t know what a “% ABV”  actually means*. Most people know something else about “strength” as well, which is that although drinking a lot of weak beer will get you as drunk as drinking rather less strong beer,  getting drunk slowly isn’t the same as getting drunk quickly.

Hence we have a simple variable called “strength” which is widely understood and is nice an easy. This concept extends way beyond beer to include all the naughty drugs – Cocaine, Ecstasy, Heroin, you name it the same logic applies, “stronger” means “higher dose” per gulp/snort/fix.

But when we come to consider cannabis we find things are measured differently and we find a new word is used: “Potency”. Whenever governments or their agencies start using a subtly different term for something you think you understand it’s always a good idea to ask why?

Last week’s blog looked at the Home Office study into cannabis potency which had a go at defining this “potency” concept. The definition the study gave was:

The potency of cannabis is defined as the concentration (%) of Δ9-tetrahydrocannabinol (THC)

Sadly it didn’t specify what the concentration is a percentage of, giving the misleading impression perhaps that a sample of herbal cannabis consists of upwards of 40% THC. Now, this is clearly not the case as a sample of herbal plant material plainly doesn’t consist of nearly half of THC, either by volume or by weight. No matter how strong the cannabis is, most of it is clearly plant material. Indeed, it’s pretty obvious that it doesn’t even consist of 5% THC by weight or volume because that would still be a huge amount of the psychoactive drug. So it’s clear that “potency” isn’t anything like the same concept as ABV.

Cannabis TrichomesAs we explained  briefly last week, the % THC figure is the proportion of the oils produced by the plant. The plant oozes oils – the pure resin – from glands known as “Trichomes” shown in the image left (from Cannabis Culture magazine).  It’s these tiny beads of oil which contain the active chemicals that make cannabis what it is and the “Potency” figure often quoted is the proportion of this oil which is THC.

Two important points flow from this:

1: Potency is not strength. Clearly you could have a sample of cannabis with very few globs of resin on, which would make it quite weak, although the resin it did contain could be high in THC, making it a high potency. Likewise a concentrated form of low potency cannabis  could deliver a large dose of THC, making it quite strong. A “concentrated form of cannabis” is known as Hashish, being the resin of the plant with far less vegetable matter included.

2: The THC is expressed as a percentage (by weight actually)  of the oils, there are clearly other substances in the oil. It turns out that one of the other substances known as CBD is very important when it comes to understanding just what cannabis does to the user.

UKCIA attended the two “Cannabis and Mental Health” conferences held in London in 2004 and 2007, you can see the reviews of them in the library section.  One of the more interesting presentations (for me) came from Dr Zerrin Atakan who was involved in a research project which finally reported last week, a short review of it can be seen here. The study undertaken by Zerrin Atakan and Professor Philip McGuire consisted of giving subjects a dose of THC or CBD or a placebo and examining the effects on the subject by both a series of standard tests and also by magnetic resonance imaging of the brain.

Professor Philip McGuire concludes, “These studies show that THC and CBD have distinct effects on brain function in humans, and these may underlie their correspondingly different effects on cognition and psychiatric symptoms.  Determining how the constituents of cannabis act on the brain is fundamental to understanding the role of cannabis use in the aetiology of psychiatric disorders.”

The really interesting thing about this is that CBD, which has never (before the recent Home Office study)  been routinely monitored turns out to be playing a significant role. Indeed, it’s almost the polar opposite of THC in its effects in some respects. If THC is linked to psychotic type episodes, CBD has anti psychotic properties. If THC is thought to cause panic attacks, CBD calms those impulses. Put in terms the Daily Mail could understand, if THC is “bad”, CBD is “good”.

The practical upshot of all this is that talking of cannabis simply in terms of “potency” is meaningless, we need a totally different and far more sophisticated way to describe it. The measure of “potency” as used by the government is simply not up to the job, which is no surprise really as it came from the law enforcement requirements of prohibition, not from concerns of public health.

Of course, all this isn’t news to experienced cannabis users. It’s long been known that the old skool hash from Morocco for example was laid back whilst some of the modern strains are somewhat “edgy” or “trippy”. But we can thank Zerrin and her team for providing the explanation  in terms of the effects of THC and CBD on the brain and providing the science behind the folk legend.

Although as we explained last week, UKCIA has serious reservations about the way the Home Office “potency” study collected its data and on its lax definitions it did show one interesting result which is relevant to this discussion; the THC/CBD balance of “traditional” hashish is very different to that of some herbal cannabis on sale in the UK. The traditional hash contained something like 5% THC and 3.5% CBD on average. Now what this means is the oils in the sample contained a total of 8.5% active ingredients and 91.5% uninteresting goo (an unknown proportion of which is probably added contamination). The valuable bit of information here isn’t the potency but the ratio of the two chemicals of 7 parts CBD to 10 parts THC. That isn’t too far off 50-50. It’s interesting to note that the composition of Sativex – the cannabis medicine – is 50/50 THC/CBD, a composition arrived at because it had the best effectivity with the minimum unplesant side efects.

The thing to note is that before the present policy followed by our government, most of the cannabis supplied to the UK was of this type. The prohibition policy so enthusiastically followed by our government has seen this replaced by strains much lower in CBD. So there we have an “unintended consequence” of prohibition, the suppression of a well balanced product and its substitution with something very different, but different in a way no-one thought important to monitor, much less control. Having caused this change in market share through the workings of prohibition, the government then uses the change to impose stronger prohibition.

With most – if not all – other drugs the control of the strength is important. With cannabis the composition in terms of THC and CBD is equally if not more important. This variable is determined primarily by the strain grown, in other words by the seeds sold.  If the government is really concerned about the potential for harm caused by the type of cannabis on sale in the country, controlling and properly regulating the seed suppliers is the way to go. Here we have some solid science to support that suggestion.

Thus far, the law has only served to make things potentially far more dangerous than it used to be whilst relying on a useless measurement which is widely misunderstood.


* % ABV means “the percentage of Alcohol by volume”, so 100 ml of 10%ABV plonk will contain 10ml of pure alcohol.