Medical cannabis is legal. That does not mean it works

Medical cannabis is legal. That does not mean it works


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Dr Alex Wodak estimates that tens of thousands have applied for legal access to medical cannabis. Photo: rmills@fairfaxmedia.com.au

Dr Alex Wodak estimates that tens of thousands have applied for legal access to medical cannabis. Photo: rmills@fairfaxmedia.com.au

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FOR medical cannabis, some experts believe the hype has surged way past the science, which is weak, inconclusive and often non-existent for many conditions.

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THESE days, when Deb Lynch reads that medical cannabis is legal, she just laughs and laughs.

“We used to get annoyed about that,” she says. “Not any more.”

Ms Lynch expected legalisation would mean she could access the drug to treat her autoimmune disease.

But, like many, she has been knocked back and told there is no evidence it would help her.

For medical cannabis, some experts believe the hype has surged way past the science, which is weak, inconclusive and often non-existent for many conditions. When cannabis does work, the effect is often small.

“The evidence, in general,” says Professor Mike Farrell, Australia’s leading medical cannabis expert, “is modest”.

Patients are left deeply frustrated.

Tens of thousands have applied for legal access to medical cannabis, mostly to treat chronic pain, estimates Dr Alex Wodak, president of the Australian Drug Law Reform Foundation. So far, only 525 patients have been approved.

“I have tried multiple doctors over the last four years to try to get a legal prescription,” says Ms Lynch, the president of the Medical Cannabis Users Association of Australia.

“I have a letter from the health minister saying there is not enough evidence. Yet I can come up with dozens of peer-reviewed studies saying it works for my condition.”

Advocates say standard methods for assessing drug effectiveness do not work when applied to cannabis. Cautious bureaucrats are restricting access to a life-saving medication, they believe.

“The community is onside, the politicians are onside, the government officials are not onside," says Dr Wodak. "Why stop these people?”

When he legalised medical cannabis in 2016, Victorian Premier Daniel Andrews said it was about getting “this life-saving treatment available to the sick kids who need it most”.

“This is too important to wait,” the Premier later said.

But waiting – waiting for the evidence to come in – is part of Australia’s drug regulation scheme.

It takes about 10 months for the Therapeutic Goods Administration to approve a new prescription medicine once its big-pharma backers submit studies proving its effectiveness.

These sort of trials do not yet exist for many things people seek to treat with medicinal marijuana. That’s why only one cannabis medication – for multiple sclerosis – has been approved by the TGA.

“We're getting way ahead of ourselves,” says Associate Professor Adrian Reynolds, president of the chapter for addiction medicine at the Royal Australasian College of Physicians.

“It’s interesting that parliament are quick to implement reforms that evidence does not yet support – and yet we provide huge amounts of evidence for things like alcohol harms, and parliament does not want to go there.”

Professor Farrell, who is director of the National Drug and Alcohol Research Centre, conducted a systematic review – considered the gold standard for evidence – on cannabis for the TGA last year.

It showed reasonable evidence the drug helped children with drug-resistant epilepsy. There was some inconsistent evidence it helped adults with multiple sclerosis.

There was good evidence it was as effective as conventional drugs for stopping chemotherapy-induced nausea – but only compared to older, superseded drugs. The evidence for patients with chronic pain was weak and the effect was, at best, modest.

“In relation to pain, most of the studies were of medicinal cannabinoids combined with other pain medications,” Professor Farrell says. “It’s quite important that people don’t have over-expectations of what it might do.”

“The data is positive, but it’s modest. The numbers needed to treat is quite high – something like eight or 10 people need to be treated for one to benefit.”

But beyond that, there is very little high quality evidence for medical cannabis. Doctors are being barraged with requests for cannabis for a huge range of other conditions where the evidence is nowhere near as robust.

A survey conducted by the Medical Cannabis Users Association showed depression/anxiety, chronic pain, PTSD, and cancer/leukaemia were the four biggest illnesses people were seeking cannabis to treat.

Professor Farrell is still reviewing cannabis as a treatment for depression and anxiety, but says “the literature on it is very thin”. In fact, other studies suggest cannabis use may increase the risk of developing anxiety and depression.

Advocates point to another review, conducted by America's National Academies of Sciences, Engineering, and Medicine, released last year. Confusingly, it found “substantial ... significant” and “conclusive” evidence for the treatment of the same conditions Professor Farrell’s study looked at.

Many studies considered by Professor Farrell’s review were randomised controlled trials, which compare a drug to a placebo and are considered the best evidence for pharmaceutical effectiveness.

Randomised-controlled trials are not the best way to assess medicinal cannabis, says Dr David Caldicott, who teaches a course on medical marijuana based at the Australian National University.

Cannabis contains dozens of active compounds – trials tend to test only one or two. It also tends to affect people differently, and tends to be effective only over a long period. These subtleties are not captured by controlled trials.

“An entire new study design is needed for cannabis,” he says. “Many of our colleagues don’t quite understand that.”

The issue has split the Royal Australian College of GPs and the College of Physicians.

“The problem with medicinal cannabis is we don’t yet have the robust evidence the general public would normally expect if not demand, and the medical profession would normally want,” says the College of Physicians' Professor Reynolds.

Doctors should only prescribe a drug when there is proof it works, he said.

“Is medicine to remain a scientific endeavour, or is it to become a personal-want-driven endeavour?”

Dr Bastian Seidel, president of the College of GPs, is far more bullish.

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