Medicinal cannabis may be garnering the majority of research attention but a new study by Monash University is investigating how the ratio of chemical compounds in the drug affects long-term recreational users. By Michele Tydd.

Nimbin’s recreational cannabis trial

Professor Murat Yücel, lead researcher from Monash University’s Turner Institute for Brain and Mental Health.
Professor Murat Yücel, lead researcher from Monash University’s Turner Institute for Brain and Mental Health.

The northern New South Wales village of Nimbin has become the focal point for Australia’s first naturalistic study of long-term cannabis use on the brain and mental health.

Researchers from Monash University are looking at participants in their own environment to see how their brain has responded over time to the levels of chemical compounds, known as cannabinoids, contained within the typical marijuana they use.

Known worldwide for its hippie lifestyle, Nimbin, along with the wider Northern Rivers area, was chosen because of its locally grown cannabis – colloquially known as “bush weed” – which has a richer cannabinoid profile compared with the hydroponically grown mass-produced cannabis available in cities.

Of particular interest is the ratio of Delta-9-tetrahydrocannabinol (THC) and cannabidiol (CBD).

The aim is to build on emerging evidence that suggests the extent to which brain-related damage manifests depends on the interactions between THC, which gets people high and has been associated with psychological and neural harm, and CBD, which purportedly has neuro-protective and therapeutic properties.

“While we have some positive preliminary findings supporting CBD’s neuro-protective role, there is still lack of clear evidence regarding whether harm associated with THC can be minimised by increasing levels of CBD,” says Professor Murat Yücel, lead researcher from the university’s Turner Institute for Brain and Mental Health.

Known as the Cannabis-Components and Brain Debate (CBD) Study, it was the only recreational cannabis study financed by the peak research funding body National Health and Medical Research Council in the past three years, with most of its cannabis funding over that time allocated to medicinal research.

The Morrison government last month acknowledged the growing interest in medicinal cannabis when it announced a $3 million grant from the Medical Research Future Fund to examine the benefits of cannabis for pain, symptom and side-effect management for cancer patients.

As necessary as this research is, Yücel says the explosion of interest in medicinal cannabis makes further recreational cannabis research even more pressing.

“The mere term ‘medicinal cannabis’ can give people the impression that cannabis is now considered to be safe for recreational use when there are still many gaps to be filled,” he says. “Addressing these gaps is both timely and important considering Australia has one of the highest cannabis prevalence rates in the world. And also there is now a shift towards more liberal policies around cannabis.”

Yücel was referring to recent laws passed by the ACT Legislative Assembly allowing individuals to possess and use small amounts of cannabis from January 31 next year.


Liam, 29, an office worker and an accomplished musician from Sydney who started smoking in his late teens, says he uses cannabis as other people would use wine.

“I was pretty hardcore when I was in my early 20s but with a full-time job and a long commute, it’s more an after-work and weekend thing now.

“It’s a bit of a wind-down, and at the same time I also find it creatively stimulating,” he says.

But Liam admits he does have some concerns about possible brain damage from long-term use.

“In the early years when I’d get together with friends, we’d have long conversations about the pros and cons. We were young and impressionable and wanted to know more about it but we didn’t really get anywhere because there didn’t seem to be much out there in terms of answers,” says Liam.

The Monash study, which is looking for about 150 volunteers, has offered participants the option to have one gram of their usual supply analysed to profile the ratio of THC to CBD.

Liam says he would welcome that sort of opportunity because he thinks the cannabis source makes a difference.

“If you want to know exactly what’s in a beer, you just dial up the brewery, but it’s not like that with cannabis,” he says. “Over the years though, I’ve sought out bush weed where possible. It just feels better and more natural than the stuff you get from some of the questionable people on the streets. I’ve bought cannabis that makes you feel really weird and strange, not like the regular stuff.

“I suppose because it’s not legal you don’t really have a right to know the chemical breakdown, but it would be helpful, even if it’s only suspected that it makes a difference.”

Liam says despite his concerns he does not feel the drug has impaired his memory or cognitive abilities to any great extent.

“I’ve had the odd time when I’ve been blitzed and I get mid-sentence and forget what I was talking about, but the same thing can happen after a few wines.”

The researcher charged with recruitment, Dr Yann Chye, says Nimbin is ideal for study purposes because of the number of people in the community who use homegrown cannabis. In comparison, people in the city are more inclined to constantly change dealers, making it hard to get a consistent sample.

“The problem with much of the mass-produced cannabis is that CBD has been almost cultivated out of the plant to boost the levels of THC,” says Chye.

“At the moment there is an average of less than 1 per cent CBD in the plant compared to 20 per cent THC. If we can understand how they interact, maybe there will be a case for standardising cannabis use with protective cannabinoid ratios.”

Monash University has obtained all required approvals to conduct the study on what is essentially an illegal drug. Those who have signed up for the study have been assured of confidentiality, but they have also been warned they participate at their own risk.

About 20 people who, according to the study criteria, have been cannabis users for at least three years are scheduled for the first phase of interviews. If they are suitable for the next stage, they will then undergo MRI scans on their brain.

“We will be looking at a variety of imaging parameters such as volume of the brain, as well as levels of metabolic compounds and resting state activity, especially in the hippocampus [the area associated with memory],” says Chye.

A control group of non-users from the same region will also be scanned for comparison.

Chye says participants she has interviewed have quite strong opinions on what they suspect certain cannabinoids will and will not do and are passionate about their views.

Most of the volunteers, in answer to why they want to participate in the study, believe not enough is being done to demystify how the plant’s cannabinoids work, she says.

The trial is expected to last two years.

“The outcomes of this study will have direct implication for public awareness and therapeutic strategies for harm minimisation and policy,” says Professor Yücel.

“These include breeding CBD back into cannabis, which is a topical and welcome notion among users where anecdotal evidence around the benefits of CBD for wellbeing is already spreading. High-CBD strains of cannabis are already being marketed in the United States.”

Liam, the long-term user from Sydney, says anything to do with making cannabis more transparent and safer would get his tick of approval.

On the other hand, he says if research links significant health issues to long-term cannabis use, “I would stop. But if it’s comparable to drinking wine or beer, I’d probably keep going.”

This article was first published in the print edition of The Saturday Paper on November 9, 2019 as "Balancing equations".

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Michele Tydd is an Illawarra-based freelance journalist.

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