A comprehensive profile of THC: from ancient medicine to modern controversy | Research

The takeaway

A thorough review of THC covers its chemistry, pharmacology as a CB1 partial agonist, approved therapeutic uses for pain and nausea, and the ongoing debates around psychosis risk, cognitive impairment, and addiction potential.

Anyone seeking a broad, authoritative overview of THC science, from students to clinicians to policymakers.

192 million users globally

What the researchers found

THC primarily acts as a partial agonist at CB1 receptors, producing its distinctive intoxication. It is approved for chronic pain, chemotherapy-induced nausea/vomiting, and MS spasticity, and is being investigated for anorexia nervosa, dementia agitation, and Tourette syndrome. Robust debates continue around its capacity to produce psychosis, cognitive impairment, and its addictive and gateway potential.

Why it matters

With an estimated 192 million cannabis users globally, understanding THC at the molecular, clinical, and societal level is essential. This review serves as a definitive reference point for the science and controversies surrounding the world's most widely used illicit psychoactive compound.

The numbers in context

192 million estimated cannabis users globally. THC available as Marinol, Sativex, and Namisol. Approved indications: chronic pain, chemotherapy nausea/vomiting, MS spasticity. Under investigation: anorexia nervosa, dementia agitation, Tourette syndrome.

How the study worked

Comprehensive narrative review covering THC chemistry, pharmacology, therapeutic uses, history, and societal context as part of the "Dark Classics in Chemical Neuroscience" series.

What this study cannot tell us

As a narrative review, this does not provide systematic evidence synthesis or meta-analysis. The breadth of topics covered means individual areas receive less depth than dedicated reviews.

How to read the evidence

Rated strong because this is a comprehensive, authoritative review published in a major neuroscience journal synthesizing decades of research.

When this study was published

Published in 2019. Cannabis research, policy, and legalization have continued to evolve rapidly since.

The bigger picture

THC occupies a unique position as simultaneously an ancient medicine, a modern pharmaceutical, and the world's most popular illicit drug. The scientific and social controversies surrounding it reflect deeper tensions about drug policy, individual liberty, and the boundaries of therapeutic evidence.

Questions still open

Will the expanding legal landscape lead to better understanding of THC risks and benefits? Can the psychosis and cognitive impairment risks be separated from therapeutic benefits through dose optimization or novel formulations? How does partial agonism at CB1 explain THC's unique pharmacological profile?

Common questions

What does THC do in the brain?

THC acts primarily as a partial agonist at CB1 cannabinoid receptors, which are found throughout the brain. This produces its characteristic intoxication, pain relief, appetite stimulation, and other effects.

What is THC approved to treat?

THC is approved for chronic pain, chemotherapy-induced nausea and vomiting, and multiple sclerosis spasticity. It is being investigated for other conditions including anorexia nervosa and Tourette syndrome.

Is THC addictive?

THC has recognized addictive potential, though the severity and prevalence of cannabis use disorder are debated. The review notes this as one of the major ongoing scientific controversies.

Read the original research

Dark Classics in Chemical Neuroscience: Δ9-Tetrahydrocannabinol.

ACS chemical neuroscience, 10(5), 2160-2175

View on PubMed ↗Publisher’s paper ↗

Citation

Banister, Samuel D; Arnold, Jonathon C; Connor, Mark; Glass, Michelle; McGregor, Iain S. (2019). Dark Classics in Chemical Neuroscience: Δ9-Tetrahydrocannabinol.. ACS chemical neuroscience, 10(5), 2160-2175. https://doi.org/10.1021/acschemneuro.8b00651