Online cannabis oils contain dangerous amounts of psychoactive THC

Although specialist doctors registered with the General Medical Council (GMC) have been allowed to prescribe cannabis-derived medicines since November 2018, a lack of research into their effects is leaving patients open to buying unlicensed products, sometimes containing over 400 times the legal limit of certain key ingredients.

THC is the psychoactive ingredient in cannabis271 EAK MOTO | Shutterstock

Leading scientists and clinicians from the University of Bath and University College London (UCL) recently published a review that describes the ranges of cannabis-derived products available and highlights the need for more information to better educate clinicians and patients about the medicinal properties of these products and their effects on the body.

Lead author of the study Dr. Tom Freeman, from the University of Bath’s Addiction and Mental Health Group explained:

In this complex and rapidly evolving field, there are several different cannabis-based and cannabinoid medicinal products. These differ in their THC and CBD content, who can prescribe them, and the conditions they may be used to treat. Here we provide an update for clinicians in advance of forthcoming NICE guidelines.”

Cannabis and its related products had been strictly regulated until new policies put into place on 1 November 2018 allowed cannabis products to be used for medicinal use in the UK, among a number of other countries.

While there have been claims that cannabis-based medications can help manage conditions such as chronic pain, multiple sclerosis, epilepsy, and the side effects associated with chemotherapy, this particular study advises that because they often “lack quality standards,” cannabis-based products sold in health shops and online “should not be used for medicinal purposes.”

Differentiating between THC and CBD

Cannabis-based products intended for medicinal uses contain cannabinoids from the cannabis plant itself, including THC (Δ8-tetrahydrocananbinol) and CBD (cannabidiol), or a combination of the two.

THC, which is just one of the 144 different cannabinoids produced by the cannabis plant, is the psychoactive ingredient in cannabis responsible for inducing the high experienced by users. By contrast, CBD is not intoxicating. Synthetically produced cannabinoids designed to produce the same effects as their natural counterparts are also used in medicinal products.

THC and CBD can have different clinical benefits when used independently. For instance, THC, when used on its own, can be effective as a treatment against nausea and vomiting induced by chemotherapy, and CBD when used independent of THC may be effective against relieving treatment-resistant epilepsy.

The therapeutic benefits of THC and CBD when used in conjunction is thought to be due to their contrasting mechanisms of action.

CBD is safer than THC

The study explains how cannabis-based products could cause harm to patients, drawing on the following example to explain their contrasting mechanisms:

CBD increased plasma endocannabinoid levels in a clinical trial in schizophrenia, which correlated with the degree of symptom improvement. When taken together with THC, CBD may offset some of the adverse effects of THC and CBD may contribute to safety as well as therapeutic effects.”

The study also states that CBD has an “excellent safety profile and is well tolerated, even at high doses.” However, THC does pose increased risks to adverse effects, with THC in particular being linked to increased risk of disorientation and dizziness.

More ‘rigorous clinical trials’ are needed

It goes on to emphasize “More larger and rigorous clinical trials are needed, including further exploration of dose-response and interactions with other medicines.”

The study claims the lack of trials investigating the effects of unlicensed cannabis products is partly due to the “regulatory challenges” that hinder research on drugs in Schedule 1.

Dr. Freeman emphasizes said “Research on unlicensed cannabis products has been limited to date. The rescheduling of cannabis and allocation of dedicated UK research funding will improve the evidence we have to guide clinical decision-making.”

CBD products that can be bought in health food shops and via the internet have their THC content legally restricted to up to 0.2 percent in the EU. However, in reality the declared amounts of THC in these non-medicinal CBD products, which are sold as herbal remedies and not regulated medicinal products, can vary widely and be misreported.

This means that some products exceed the legal limit set by the EU. Additionally, their CBD content can be lower than in clinical trials.

Cannabis oils bought online often contain the psychoactive ingredient, THC

An undercover reporter for the Daily Mail posed as a father on Facebook groups where parents discuss using cannabis oils to treat their children for a range of conditions. Within these discussions were links to a number of dealers who had posted adverts for “Full spectrum high quality THC oil”.

The cannabis oils the reporter was able to buy online had THC levels in excess of 80 percent, discovered through laboratory tests.

Additionally, sellers were free to make unsubstantiated claims about what their cannabis oils could treat, leaving parents trying to alleviate their children’s conditions vulnerable not only to exploitation, but also to the increased risk of serious complications caused by unregulated products.

A “60ml course” of cannabis oil was offered to the Daily Mail reporter for £1,500, and edible “sweets” for £25.

Packages containing the cannabis products were often disguised as gifts to be posted to buyers, and TicTac Drug Identification laboratory in London found that one sample contained 86 percent THC and a low level of CBD.

Neurologist Professor Orrin Devinsky, who is a world-leading expert on cannabis-derived medication for childhood epilepsy, warned parents against giving the high THC cannabis oils to their children, saying:

“It’s not something that we have safety and efficacy data on. When [the medicine] is high in THC, we know it can have psychiatric effects.”

Co-author of the study published for the BMJ Dr. Michael Bloomfield, Head of Translational Psychiatry at University College London, spoke on the benefits of the new study.

There have been leaps and bounds in our scientific knowledge in recent years, which combined with confusing claims about the medicinal uses of these drugs can be potentially perplexing for doctors and patients. We hope that our new guidance is helpful to doctors and patients worldwide. Much more research is needed into this new class of medicine.”

Dr. Chandni Hindocha of the Clinical Psychopharmacology Unit at UCL, another co-author of the study reinforced the need for more research, stating,

“Resources must be made available to update and educate clinicians about cannabis and cannabinoid-based medicines.

We would like to encourage doctors to maintain a compassionate and evidence-based approach when engaging with their patients in this rapidly developing field, in order to provide the best standard of care.”


Medicinal use of cannabis based products and cannabinoids. BMJ 365:l1141. 4 April 2019.

Lois Zoppi

Written by

Lois Zoppi

Lois is a freelance copywriter based in the UK. She graduated from the University of Sussex with a BA in Media Practice, having specialized in screenwriting. She maintains a focus on anxiety disorders and depression and aims to explore other areas of mental health including dissociative disorders such as maladaptive daydreaming.


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