October 2016.

Is there any reliable evidence for cannabis as a cure for different diseases? If there is, will British doctors be allowed to prescribe it?

1 answer

The main thing to understand is that cannabis is an unbelievably complex drug. It's got something like 545 chemical compounds, of which 104 are cannabinoids. And pretty much all of those potentially could have medical uses. It's got a lot going on!

But within that, the main chemical that's been investigated and seems to be most interesting from a medical perspective is what's generally called THC – that's tetrahydrocannabinol, or more properly delta-9-tetrahydrocannabinol – and that seems to be primarily picked up in the nervous system throughout the body by pathways that are associated with pain. And that seems to be the best evidence for an actual valid medical use right now. There is randomised controlled trial data to support its use in managing pain.

Now of course pain is a hugely complex phenomenon, it's not just about a simple signal arriving in your body, there's a huge brain component – a cognitive component – in pain. So understanding how something operates on pain is never simple. But there is definitely evidence for a potential role for the psychoactive components in cannabis as a pain management tool, especially with chronic pain. When people have ongoing, persistent pain, whether as a result of injury or illness, it can be very resistant to traditional painkillers – which traditionally ends up taking people off in the direction of opioids, where of course there can be other, very severe problems coming in.

There are other beneficial effects which are claimed for other cannabinoids, but these are far less clear and studies are often showing conflicting results. That’s to be expected with something this complex, as often you'll see something different if you study regular cannabis users than you do if you start isolating compounds and testing those. It's entirely likely that other bona fide uses will come through – but right now, the pain management aspect is the one thing where we can point to fairly good, well-controlled studies and say, yes, this has a use.

Will it be licensed in this country? Who knows? It's never a simple decision. Canada, for example, just made medical cannabis legal, then immediately ran across the problem that it was still illegal to actually produce it. More significantly, this isn't really a scientific or medical question, so much as one about society's views on drugs. It's entirely dependent on what government is in power, and given the record of the current one, I wouldn't put my hand on my heart and say it'll be happening any time soon. 

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