Cannabis and mental health: more grey than black and white

Concerns have been raised about the lack of knowledge of the benefits and harms regarding cannabis and mental health

In the UK there is strong public and political support for medical cannabis being available to patients who can benefit from it. As far back as 2016, a Populus poll found that 68% of the UK population supported the idea and last year’s change in the law to legalise medical cannabis in the UK was met with widespread political and public acclaim.

However, the fear that cannabis, even in its medical form, might be harmful still stalks much of the debate, particularly in the popular media – which makes links to mental disorders such as psychosis and schizophrenia.

Cannabis and mental health

Many health professionals are still concerned about safety which has, in part, led to the current unwillingness of NHS clinicians to prescribe the newly legalised compounds. So with many patients reporting that they consume medical cannabis to help with a wide range of health conditions, including alleviating the symptoms of mental health issues, we are in the paradoxical position that some people consume cannabis to help improve a mental health condition, whilst others view such consumption as a cause of those mental health issues, not a cure.

Media bias

Some aspects of the popular media delight in blaring out: ‘Consuming cannabis can lead to psychosis and even schizophrenia.’ Other ‘cannabis campaigners’ have an equally entrenched view that this is not the case.

The real situation is more nuanced than either of these positions. Having a debate based on such polarised views helps neither the public nor the medical professionals.

The true picture can only be ascertained by looking at evidence. For example, there is some new evidence around the effectiveness of CBD, a non-intoxicating cannabinoid found in cannabis, helping people live with schizophrenia. The randomised-control trial published in the American Journal of Psychiatry, funded by GW Research and the National Institute for Health Research showed that after six weeks of treatment, the group treated with CBD had lower levels of psychotic symptoms, and were more likely to have been rated improved and not as severely unwell by a clinician.

Limited evidence

This evidence is currently limited in scope, however, it should open the door for developing more evidence around this particular link, and also for securing evidence of efficacy or otherwise across a broader range of health issues, both physical and mental.

Stating that cannabis may contribute to symptoms of schizophrenia-like psychosis is an easy narrative because it’s been perpetuated for so long. What’s more difficult is employing rigorous science and the nuances required to have an evidence-informed discussion on this topic.


While a link exists between cannabis and psychosis, it exists mostly for people who are heavy users of THC products and who have a predisposition to psychosis. In fact, one recent study suggests that genetics could account for about 69% to 84% of the link between cannabis and psychosis. It also bears mentioning that a majority of cannabis consumers experience neither psychosis nor go on to develop schizophrenia.

Further, from self-report surveys, research shows 19% of adult cannabis users were daily or near-daily users – i.e., those at the highest risk. This means that a majority of individuals who use cannabis are not doing so in ways that would potentially put them at risk for these commonly discussed, severe health issues.  The frequency of use of THC, and starting cannabis at a younger age, are also important risk factors for developing psychosis.

Framing the narrative

The narrative around psychosis and cannabis often ignores the importance of the varying social and structural factors that we know shape health outcomes. These factors have been essentially disregarded in this wider conversation around risk – things such as poverty or childhood trauma and abuse – many of which also increase levels of stress, a known risk factor for psychosis.

Unless the pressure to stigmatise cannabis is resisted and, by implication, cannabis-based medicines, and champion the role of solid evidence-based analysis we risk allowing the development of medical cannabis to be stunted.

That would be a tragedy for the potential patients and a failure on the part of the body medical, civic and political to explore all options that can help improve quality of life.

Dr Caroline MacCallum
Clinical instructor in the Department of Medicine at UBC
Medical director at Greenleaf Medical Clinic

Dr. Jenna Valleriani
CEO National Institute for Cannabis Health and Education
Executive Director Hope for Health Canada

Caroline MacCallum is an internal medicine specialist with expertise in complex pain and cannabis, a clinical instructor in the Department of Medicine at UBC, and medical director at Greenleaf Medical Clinic. Jenna Valleriani is the CEO of the National Institute for Cannabis Health and Education, and executive director of Hope for Health Canada.

Dr MacCallum will be presenting at Medical Cannabis: What UK Doctors Need to Know being hosted by Sapphire Medical Clinics on the 29th October in London. To attend please register for your free ticket here.

A version of this opinion editorial was originally published in the Globe and Mail.

Full article here.

TheGrowthOp- This cannabis spray can help with cannabis addiction

Dr. Caroline MacCallum, a Vancouver-based Complex Pain & Cannabinoid Clinician, does the math in a tweet showing that the nabiximol therapy, for the doses given within the study, would cost $29,200/year while the 1:1 cannabis oil treatment in equivalent doses would be $5913/year.

Dr. MacCallum further discusses in the thread her experiences in clinic, where she frequently uses 1:1 oil, a balanced ratio of THC to CBD from Canadian federally license producers, to treat cannabis addiction with success.

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The Cannabis-Psychosis Debate is being driven by fear mongering, not facts

“While a link exists, it exists mostly for people who are heavy users of THC products and who have a predisposition to psychosis. In fact, one recent study suggests that genetics could account for about 69 per cent to 84 per cent of the link between cannabis and psychosis. It also bears mentioning that a majority of cannabis consumers experience neither psychosis nor go on to develop schizophrenia.”

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The Walrus- Pot Is Legal. Is It Time to Redefine Sobriety?

“There’s a huge stigma,” for people who are interested in using things like cbd in their recovery, says Caroline MacCallum, a doctor and the medical director of Greenleaf Medical Clinic in Langley, British Columbia, which helps assesses patients across Canada for their eligibility under Health Canada’s Access to Cannabis for Medical Purposes Regulations. She explains that some research has shown cbd is not addictive and notes that many addictions play on the brain’s reward system. cbd doesn’t do that. Since that’s the case, MacCallum asks, could it be as benign as an antidepressant? “Some people would say sobriety is zip, zero, nothing. But that’s a tough act to follow,” says MacCallum, adding that a person’s recovery journey is between them and their physician to decide. “I think it’s really important to treat the whole person, and if somebody’s struggling.…I would want to set [my patients] up to win.”

See full article here.

Maclean's- Are there any after-effects or hangovers to cannabis?

So who’s right? “It all depends on how you’re using it and if you’re using too much,” says Dr. Caroline MacCallum, medical director of Greenleaf Medical Clinic in Vancouver. A medical patient, for example, will likely start with 1 to 2.5 mg dose of THC, slowly build up their tolerance and never experience a weed hangover. “But it’s different for a recreational user,” she says, “because they’re targeting a euphoric state and using more THC to get there.” You can’t dose any product if you don’t know what’s in it, she warns, and while most strains’ THC level falls between two and 20 per cent, others like the infamous shatter can contain up to 80 per cent. Oils and edibles are worse—both in their excessive potency and because impatient users tend to re-dose before effects kick in. MacCallum recently saw a brownie with 400 mg of THC, which is 200 times what she’d prescribe.

Just like every other hangover, the more you consume, the more likely you are to suffer after-effects. Though she’s only encountered it a handful of times, MacCallum says patients complain of mental fog, slowness and fatigue. Compare this to pounding headaches and vomiting caused by alcohol, however, and maybe a stoned-over is not so bad. “It’s not the same as alcohol, it’s not even the same as Benadryl,” says MacCallum, who notes many patients prefer cannabis to other sleep meds.

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CBC- Phasing out medical cannabis would leave pediatric patients in the lurch

By: Jenna Valleriani & Caroline MacCallum, September 8, 2018 for CBC News

Physicians in Canada are prescribing cannabis. They have been doing so for years, and will likely continue to do so after recreational cannabis is legalized this fall. But the Canadian Medical Association (CMA) says that doctors in Canada want to see the phasing out of the medical cannabis access program once pot is legalized. And no doubt, some do…

The CMA's position on cannabis for medical purposes is that there is "insufficient evidence on risks and benefits, the proper dosage and potential interactions with other medication." However, this view ignores thousands of peer-reviewed journal articles and studies that provide evidence of the efficacy of cannabis use for some medical conditions — chronic pain, as one example. While we do not deny that more clinical studies are needed, surely the publishing of over 10,000 peer reviewed articles signals that the use of cannabis in medical treatment is not some fringe endeavour.

There are numerous risks in eliminating a medical stream of cannabis access — risks that include things like the loss of guidance around dosing and administration, contraindications to cannabis use, screening for dependency risk and potential drug interactions. Essentially, it ignores the realities physicians are facing on the ground.  

But there's one critical topic that has been left completely out of consideration regarding the issue of narrowing cannabis access to just the recreational stream: youth under the legal age of access…

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Canadian Living- 5 common myths and misconceptions about cannabis use

As cannabis is legalized in Canada, we know you have questions—and we know there’s a lot of misinformation out there. We sat down with two doctors to chat about cannabis usage. 






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How Canada legalising recreational marijuana could vault country to forefront of cannabis research

Medical marijuana studies are set to explode in Canada after the use and sale of cannabis become legal in October. It is only the second country, after Uruguay, to fully legalise the drug for recreational purposes

Caroline MacCallum, a Vancouver-based internal medicine specialist, has focused on complex pain at a number of hospitals. She is a clinical instructor at UBC’s faculty of medicine, and the medical director for Greenleaf Medical Clinic, where she’s assessed and developed cannabinoid treatment plans for more than 2,000 patients using legal medical cannabis approved by Health Canada.

MacCallum says she embraced marijuana when she was working as a pharmacist, noting that patients with complex chronic diseases had sometimes tried between 10 and 20 different medications looking for relief.

“There is very little, if any, education about cannabis in most medical schools,” she says. “I think that is changing, or will need to. I have medical students, residents and fellows who spend a few days with me in the clinic to learn about medical cannabis.

“But there’s definitely a place to learn more formally about the science of the endocannabinoid system, and also practical clinical knowledge about [cannabinoids] CBD and THC dosing, routes of administration, evidence, contraindications (withholding treatment because it’s harming the patient), monitoring, side effects, product safety and consistency, and more.”

July 15, 2018 as seen on South China Morning Post.

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Arthritis Society to launch employer toolkit for medical cannabis coverage

As a forward-thinking advocate for the needs of Canadians living with arthritis and related chronic pain conditions, the Arthritis Society today announced that it is leading the way by introducing a program and toolkit to help employers cover the costs of cannabis for medical purposes for employees through their company-sponsored employee benefit plans.

The Arthritis Society has worked with a team of well-recognized patients, physicians, benefits consultants and other experts in the field to help develop the program. As of February 1, 2018, the Arthritis Society is providing medical cannabis coverage for its employees, their spouses and dependents, under its employee health benefits plan. Under the program, the Arthritis Society will provide coverage up to $5,000 per year, which is a meaningful level of reimbursement for a broad range of health conditions including chronic pain.

Dr. Caroline MacCallum prescribing physician:

I am optimistic that other employers will follow the Arthritis Society’s lead by adopting similar, inclusive, medication benefit programs. This will continue to reduce the stigma of medical cannabis, and more importantly improve access and affordability for safe supply of medical cannabis for those living with chronic pain.

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