Medicinal cannabis seems like one of the health topics du jour but it has a long history grounded in medical research. In 1841, an Irishman named William Brooke O’Shaughnessy noticed folk use of cannabis as a medical treatment in Calcutta.

O’Shaughnessy was so fascinated by this that he studied its use and effects. He was the first person to officially introduce cannabis into Western medicine via a scientific paper: in 1843, his paper titled ‘On the preparations of the indian hemp, or gunjah’ was published in The British Medical Journal (then known as The Provincial Medical Journal and Retrospect of the Medical Sciences).

O’Shaughnessy was born in Limerick in 1809 and studied in Trinity College Dublin before moving to Scotland and studying forensic toxicology and chemistry. After failing to obtain a position of Professor of Medical Jurisprudence in the University of London, he joined the East India Trading Company and moved to Calcutta. While there, he discovered folk use of cannabis and validated some of the treatments.

He gained a reputation by discovering new applications of cannabis use including treat infants suffering from convulsions and pain pain relief from rheumatism. Thanks to O’Shaughnessy, cannabis became a very popular treatment in Victorian Britain for various ailments.

O’Shaughnessy’s research note that cannabis (or hemp) appeared to have many applications: “Hemp possesses, in small doses, an extraordinary power of stimulating the digestive organs, exciting the cerebral system, of acting also on the generative apparatus.

‘Larger doses, again, were shown by the historical statements to induce insensibility or to act as a powerful sedative. The influence of the drug in allaying pain was equally manifest in all the memoirs referred to.’

He also wrote that, in his opinion, the side effects of cannabis as noted by other researchers at the time, were exaggerated. “[The side effects] did not appear to me so numerous, so immediate, or so formidable, as many which may be clearly traced to over-indulgence in other powerful stimulants or narcotics – viz, alcohol, opium, or tobacco.”

Cannabis: legal since until 1928

Back then, little was known about this plant and its various chemical properties. Now we know that cannabis is made up of a number of cannabinoids, a specific family of chemical compounds, which include cannabidiol (CBD) and Tetrahydrocannabinol (THC) as well as other compounds known as terpenes and alkaloids. This is a lot of ingredients and they all have various different effects.

THC is the psychotropic constituent in cannabis that gets you high while CBD is thought to have potential therapeutic effects. In fact, cannabis was used in Ayurvedic medicine, an ancient system of medicine based in India. It wasn’t used on its own as those who practiced believed that it altered the balance between mind and body. It was used in conjunction with other treatments for ailments ranging from diarrhoea to sexual dysfunction.

Cannabis wasn’t made illegal in the UK until 1928 when it was added to the Dangerous Drug Act. However, doctors could still use it for medical purposes up until 1971. This sparks an interesting line of thought. Cannabis was until recently, consistently described as the “gateway drug” which would lead to more dangerous drug use. If Nixon and his war on drugs hadn’t been so set against cannabis, medical advancements with it could have come a lot sooner.

Irish government fears legalisation is for recreational use

Recently a bill proposed by Gino Kelly TD of People Before Profit which aimed to legalise the use of cannabis for certain medical conditions was rejected by the Oireachtas Health Committee. This rejection marked another twist in the journey of medicinal cannabis. The Health Committee feared that the bill put forward would legalise cannabis for recreational use rather than be used just for medical purposes. As it stands, the general consensus is that medicinal cannabis can aid in the treatment of multiple sclerosis and for the treatment of nausea induced from chemotherapy. In both of these cases, the treatment is a last resort when no other recognised treatment appears to be helping. However, in November of this year the Irish government said they would not oppose the bill meaning it can proceed to the next legislative state.

In 2016 the Barnes Report was commissioned by the UK government in order to investigate the potential therapeutic effects of cannabis. The report concluded that there is good evidence that medicinal cannabis is of therapeutic benefit for the treatment of chronic pain, chemotherapy-induced nausea and anxiety management. It also found moderate evidence for the treatment of sleep disorders and some symptoms of Parkinson’s Disease, but no convincing evidence of the effects of cannabis on tumour growth in cancer or depression.

The implications of this report are interesting. Firstly, cannabis use for management of pain is a very attractive feature. Our current methods for treating pain involve prescribing opioids like morphine or Vicodin. These are highly addictive and have a dropout rate of a approximately 33%. One of the most common side effects is constipation which get worse with increased use of opioids and often a major reason for people to stop taking them.

Withdrawal symptoms from opioids are notoriously horrific. Increased use is also common as we build up tolerance to opioids which results in us needing higher doses of the treatment to work and can result in overdose. Both of these situations are exemplified perfectly in the drama series House where Hugh Laurie takes larger and larger doses of Vicodin throughout the series. The increased use causes problems with House’s kidneys but his withdrawal symptoms often result in horrible hallucinations as well as depression and insomnia.

Cannabis on the other hand has a dependency rate of 9% and less associated side effects. This makes it an attractive treatment but there are some caveats to that. There is a documented link between cannabis use and the development of psychosis as shown by McGuire and colleagues in 1995. Their report found that people with a first degree relative (parent, sibling) suffering from schizophrenia are 10 times (7%) more likely to induce schizophrenia by smoking cannabis compared to people who don’t (0.7%). These figures are low but should not be ignored. Cannabis has also been documented to affect brain development in young people so this also must be taken into account when it comes to treating children with severe forms of epilepsy like Dravet Syndrome.

No evidence to support cannabis as cancer treatment

The second interesting point to be taken away from the report is the lack of evidence for medicinal cannabis in treating cancer. This point is hard to gauge as long term studies of cannabis are hard to do since the standardisation of the treatment is difficult. Essentially much of the research done in the 1980’s weren’t using the same strain of cannabis so we cannot be sure of results, hence the need for retesting and examination of evidence.

Theoretically, cannabis might be able to control cancer cell growth or it could kill cancer cells in a lab but that doesn’t mean it can do it in the body. Cancer is an umbrella term that means “uncontrolled cell growth”. Breast cancer is different to pancreatic cancer or mouth cancer as the tumour is there but it can be caused by different things. We must therefore be careful about saying “cannabis helps cancer”. It might do, but the scientific evidence isn’t there to back that up yet and more work needs to be done in that area.

The problem now is that if you google “can cannabis cure cancer” you will inevitably come up with scores of websites offering false hope. These types of websites tell people that big pharma companies such as Pfizer are covering up the potential curative effects of cannabis. They prey on desperate people who fear chemotherapy and are looking for any sort of alternative treatment. As mentioned above, cannabis contains a number of ingredients and the interactions between these ingredients can be different depending on the condition being treated and the ratio of the ingredients to each other.

My own mother suffers from cancer and while she believes in chemotherapy, she has heard stories of other people who are flying to Germany to get their bloods changed at a cost of €15,000 and insist that cannabis oil is the cure. These people are being misled by others who either don’t understand the evidence such as the Barnes report or don’t want to. The whole point is there isn’t enough evidence to suggest that cannabis actually prevents tumour growth. Cancer is a terrible enough condition without people trying to make money off of it.

It seems that both William Brooke O’Shaughnessy and Victorian Britain were ahead of their time. They realised the potential benefits of cannabis but also validated their observations. If we are truly serious about using cannabis as a treatment for conditions such as MS or anxiety, then it needs to be tested strenuously like every other medical treatment. That being said, if Ayurvedic medicine was using cannabis to treat sexual dysfunction, the US army should consider this for their medical budget. It’s cheaper than Viagra, and a lot more fun too.

Rachel O’Neill – Editor

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