A message from Dr Simon Erridge, Research Director at Curaleaf Clinic
At Curaleaf Clinic, we’re committed to providing the highest standard of medical cannabis care, guided by science. As such, we are concerned about the growing number of people buying cannabis from illegal sources, including online platforms.
These unregulated products can pose serious health risks, and we have set out to research these risks further in collaboration with Manchester Metropolitan University. Our research has uncovered alarming levels of contamination in street cannabis, including mould, bacteria, heavy metals, and dangerous chemicals.
This report is a call to action for the public, healthcare professionals, and policymakers to take action on cannabis safety. 1.8 million adults in the UK are currently estimated to use illicit cannabis to self-treat their health conditions. Everyone deserves to make informed choices about their health and by choosing legal medical cannabis, eligible patients can access regulated products, protecting them from the potential harms highlighted in this report.
We hope this research encourages a shift towards responsible, legal cannabis use and encourages policymakers to address this growing public health concern.
What we found:
Our report combines data from several sources, including laboratory analysis of 60 illegal cannabis samples obtained in the UK, surveys of current cannabis consumers, and data from the Welsh Emerging Drugs database (WEDINOS).
Cannabis Testing with Manchester Metropolitan University
We collaborated with Manchester Metropolitan University to analyse 60 illegal cannabis samples obtained from the Greater Manchester and Tyne-and-Wear regions.
- 90% of these illicit samples contained contaminants, including mould, yeast, lead, E.coli, or salmonella, which have the potential to pose serious health risks, particularly for those with weakened immune systems.
Welsh Emerging Drugs database
WEDINOS provides an anonymous drug testing service to people across the UK. We reviewed 33,726 data entries, of which 1,635 were thought to be cannabis by the purchaser:
- 43% of these 1,635 samples contained no naturally derived cannabis compounds, meaning they didn’t come from the cannabis plant.
- 38% of these samples contained harmful substances not naturally found in the plant. Among these, 27% contained synthetic chemicals like Spice or K2, which mimic the effects of cannabis but can cause serious health problems, including heart rhythm changes, vomiting, behaviour changes, and even death.
Consumer Survey
In August 2024, we partnered with Opinium to conduct a consumer survey of 500 UK cannabis users. The findings revealed:
- Many illicit cannabis consumers are using it for health reasons. Whilst 66% consume it recreationally, 35% use it to manage symptoms caused by diagnosed medical conditions like anxiety, depression, and chronic pain.
- 23% use illicit cannabis to self-manage undiagnosed or self-diagnosed conditions.
- Many respondents purchase cannabis illegally every week (35%) or monthly (21%) but are unaware of the potential health risks (66%).
A Call to Action:
As individuals continue to use illicit cannabis to self-treat health conditions, it’s critical to raise awareness about the availability of legal medical cannabis. By making informed decisions, patients can access regulated cannabis products alongside the support of a doctor.
We hope this report encourages consumers to think carefully about the risks of illicit cannabis and if eligible explore safer, legal alternatives through medical channels. Policymakers must also consider tightening regulations to protect public health from the dangers of the unregulated cannabis market.
Discover more by reading the full Curaleaf Report:
Jump to sections:
- Implications for Public Health and Consumer Safety
- Implications for Policymakers
- Implications for the Cannabis Industry
Research Spotlight
Complementing our findings, a separate 2025 study by the University of Bath identified similar risks in the illicit cannabis market. The research revealed that many illicit cannabis edibles in the UK contain inconsistent THC levels, reflecting our concerns about dosage unpredictability, and in some cases, synthetic cannabinoids.
