Cannabis has a long history as a medicinal plant, says David Nutt in this extract from his new study

WHY IS CANNABIS SO CONTROVERSIAL?

Really, cannabis is just another plant. It’s a relative of the common hop used in beer, and it evolved around 28 million years ago on the eastern Tibetan Plateau. Cannabis has been cultivated by human beings for 6,000 years, first for food and fibre, then later as a medicine and an intoxicant.

Looked at from the perspective of these thousands of years of humans and cannabis living happily alongside each other, the roughly 100 years of prohibition has been but a blip in time.

So why have we spent so long banning it all over the world? For most of the twentieth century, we were told that cannabis was dangerous, responsible for crime and a gateway drug to “hard” drugs like heroin. One of the key anti-cannabis campaigners in the 1930s, Harry Anslinger, head of what was then the Federal Bureau of Narcotics in the US, said, “Marijuana is an addictive drug which produces in its users insanity, criminality, and death.” He used race and fear as weapons in his crusade against cannabis.

Eighty years later the UK prime minister Gordon Brown called it “lethal”. The reason, of course, is THC (tetrahydrocannabinol), the chemical in cannabis that gets you high. The paradox is, it’s THC that also accounts for a lot of the plant’s medical effects. THC is known to reduce nausea and vomiting from chemotherapy, stimulate appetite, reduce pain and spasticity and treat anxiety and insomnia.

Cannabis also contains hundreds of other plant chemicals called cannabinoids – the one you’ll have heard of is CBD (cannabidiol). At high doses, CBD can be a powerful anti-epilepsy treatment. At lower doses it can reduce anxiety and improve sleep.

As we learn more about cannabis, we’re discovering that it’s the combination of these cannabinoids and other active chemicals that together accounts for its powerful and wide-ranging medical effects.

When cannabis was first farmed, in 4000 BC in China, it was as a food – for its seeds and oil – as well as the plant fibre being used to make paper, rope and fabric. This original version of cannabis had low levels of THC, making it more like the modern hemp plant than the kind people smoke.

It’s lost to history how people discovered its intoxicant and medical properties. It’s not clear if people bred cannabis to increase its levels of THC, or if particular growing conditions led to a more psychoactive version. It’s likely it was a combination of both.

Evidence of the first use of cannabis for psychoactive purposes has been discovered at a burial site dating to around 2,500 years ago. The archaeologists who examined the site think it was burned in wooden braziers in an enclosed space as part of the burial ceremony.

We do have written evidence of cannabis being our oldest medicine. It comes from China and it’s found in the world’s first pharmacopoeia, the Pen-ts’ao Ching, which is thought to be 5,000 years old. It describes cannabis as being used for over 100 conditions, including gout and rheumatic pain. In fact, the Chinese character for anaesthesia is the same as the one for cannabis intoxication.

The spread of the cultivation of cannabis followed trade routes until it covered most of the globe, along the way becoming integrated into both religious and medical practices.

In India, it was used in medicine as a painkiller, anticonvulsant, anaesthetic, antibiotic and anti-inflammatory. And in one of the ancient Vedic scriptures, it was named as one of the five sacred plants.

Evidence has also been uncovered of cannabis being used in Persian and Arabic medicine, and of its use across Africa and South America too. It had a wide range of uses, reflecting its safety as well as its versatility as a herbal medicine. You could see this as good news for the many conditions it’s being tried and researched for in the present day. They included healing wounds; soothing pain including toothache, headache, earache and labour pains; and helping with epilepsy, anxiety, infection, malaria, fever and dysentery.

During the Middle Ages, it’s been shown that cannabis was grown in the UK. But probably due to the climate, it wasn’t psychoactive. It was hemp, grown for its hard-wearing fibres, the best source of raw materials for the manufacture of maritime rope and sailcloth. In 1535, as Henry VIII was building his navy, he passed a law requiring all farmers to grow a quarter of an acre of hemp for every 60 acres they farmed.

There are descriptions of cannabis with psychoactive properties being brought back by travellers to the East around this time. Nicholas Culpeper, in his Herbal (1653), recommended it for earache and jaundice and also wrote that the roots, “allayeth inflammations, easeth the pain of gout, tumours or knots of joints, pain of hips.”

So how did such a useful plant turn into a pariah?

It was the increasing popularity of cannabis – as an intoxicant and a medicine – in Europe during the Victorian age that sowed the seeds of prohibition.

This is an extract from Cannabis (Seeing Through the Smoke): The New Science of Cannabis and Your Health (Yellow Kite, £16.99)

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