Applying machine learning to international drug monitoring: classifying cannabis resin collected in Europe using cannabinoid concentrations

Tom P. Freeman, Edward Beeching, Sam Craft, Marta Di Forti, Giampietro Frison, Christian Lindholst, Pieter E. Oomen, David Potter, Sander Rigter, Kristine Rømer Thomsen, Luca Zamengo, Andrew A. Cunningham, Teodora Groshkova, Roumen Sedefov

Research output: Contribution to journalArticlepeer-review

1 Citation (SciVal)

Abstract

In Europe, concentrations of ∆9-tetrahydrocannabinol (THC) in cannabis resin (also known as hash) have risen markedly in the past decade, potentially increasing risks of mental health disorders. Current approaches to international drug monitoring cannot distinguish between different types of cannabis resin which may have contrasting health effects due to THC and cannabidiol (CBD) content. Here, we compared concentrations of THC and CBD in different types of cannabis resin collected in Europe (either Moroccan-type, or Dutch-type). We then tested the ability of machine learning algorithms to classify the type of cannabis resin (either Moroccan-type, or Dutch-type) using routinely collected monitoring data on THC and CBD. Finally, we applied the optimal algorithm to new samples collected in countries where the type of cannabis resin was unknown, the UK and Denmark. Results showed that overall, Dutch-type samples had higher THC (Hedges’ g = 2.39) and lower CBD (Hedges’ g = 0.81) than Moroccan-type samples. A Support Vector Machine algorithm achieved classification accuracy exceeding 95%, with little variation in this estimate, good interpretability, and plausibility. It made contrasting predictions about the type of cannabis resin collected in the UK (94% Moroccan-type; 6% Dutch-type) and Denmark (36% Moroccan-type; 64% Dutch-type). In conclusion, we provide proof-of-concept evidence for the potential of machine learning to inform international drug monitoring. Our findings should not be interpreted as objective confirmatory evidence but suggest that Dutch-type cannabis resin has higher THC concentrations than Moroccan-type cannabis resin, which may contribute to variation in drug markets and health outcomes for people who use cannabis in Europe.

Original languageEnglish
JournalEuropean Archives of Psychiatry and Clinical Neuroscience
Early online date21 May 2024
DOIs
Publication statusE-pub ahead of print - 21 May 2024

Data Availability Statement

For data requests, please contact the corresponding author.

Funding

This research was supported by a EU4Monitoring Drugs project awarded to TPF, funded by the European Union, and implemented by the EMCDDA.

FundersFunder number
European Commission

Keywords

  • Cannabidiol
  • Delta-9-tetrahydrocannabinol
  • Drug policy
  • Psychiatric disorders

ASJC Scopus subject areas

  • Psychiatry and Mental health
  • Pharmacology (medical)
  • Biological Psychiatry

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