A Review of THC's Therapeutic Potential and the Challenges That Limit Its Medical Use | Research

The takeaway

THC shows wide-ranging therapeutic potential across multiple conditions, but psychoactive side effects, tolerance development, and dependence risk continue to limit its clinical application.

Read this if you want a broad overview of what THC does in the body and why it's both promising and problematic as medicine.

Whole cannabis extract outperformed isolated THC in some therapeutic comparisons

What the researchers found

This review covered the pharmacological landscape of THC as of 2007, drawing on clinical trials, animal studies, and anecdotal reports.

The evidence supported THC's therapeutic applications across several areas including pain relief, nausea suppression, appetite stimulation, neuroprotection, and anti-tumor effects. The discovery of the endocannabinoid system (CB1 and CB2 receptors and their natural ligands) had enabled more targeted research into these applications.

However, the review noted persistent barriers: psychoactive effects in patients, adverse reactions reported in human trials, tolerance development with repeated use, and potential dependence. These issues pushed researchers toward alternative strategies, including drugs that modulate the endocannabinoid system indirectly rather than activating cannabinoid receptors directly.

Intriguingly, emerging evidence suggested that whole cannabis extracts sometimes outperformed isolated THC, hinting at synergistic effects between cannabis compounds.

Why it matters

This review captured a pivotal moment in cannabinoid pharmacology when the field was shifting from studying THC in isolation toward understanding the broader endocannabinoid system and whole-plant preparations. The observation that whole extracts sometimes work better than pure THC foreshadowed the "entourage effect" concept.

The numbers in context

The review covered applications in pain, nausea, appetite, neuroprotection, and cancer. Whole cannabis extract showed benefits beyond those of isolated THC in some comparisons.

How the study worked

This was a narrative review of the published literature on THC pharmacology, covering cellular and molecular mechanisms, animal model results, and clinical trial data. The author organized findings by therapeutic application and discussed limitations and future directions.

What this study cannot tell us

As a narrative review, it did not use systematic search methods or meta-analytic techniques. The evidence base in 2007 included many small studies and animal models with limited human clinical trial data.

How to read the evidence

This is a narrative review of the literature as of 2007, providing a broad but non-systematic overview of THC pharmacology.

When this study was published

Published in 2007. Significant advances have occurred since, including FDA approval of CBD-based Epidiolex (2018) and expanded clinical trials of cannabinoid medicines.

The bigger picture

The tension identified in this review between THC's therapeutic promise and its side effect profile continues to drive cannabinoid research today. The pivot toward endocannabinoid system modulators and whole-plant medicines has since yielded approved medications like nabiximols (Sativex) and prescription CBD (Epidiolex).

Questions still open

What specific compounds in whole cannabis extract contribute to therapeutic effects beyond THC alone? Can endocannabinoid system modulators achieve therapeutic benefits without THC's psychoactive effects?

Common questions

What is the "entourage effect"?

The idea that whole cannabis extracts containing multiple compounds (THC, CBD, terpenes, etc.) may produce therapeutic effects that exceed what any single compound achieves alone. This review noted early evidence for this concept.

Why can't THC just be used as medicine like any other drug?

THC produces psychoactive effects (the "high"), and patients can develop tolerance (needing more for the same effect) and dependence. These issues make dosing and long-term use more complicated than with many conventional medications.

Read the original research

On the pharmacological properties of Delta9-tetrahydrocannabinol (THC).

Chemistry & biodiversity, 4(8), 1664-77

View on PubMed ↗

Citation

Costa, Barbara. (2007). On the pharmacological properties of Delta9-tetrahydrocannabinol (THC).. Chemistry & biodiversity, 4(8), 1664-77.