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How researchers grow medical-grade cannabis for clinical trials, from breeding to extraction

ReviewModerate evidence
The takeaway

Two leading institutions, GW Pharmaceuticals and the University of Mississippi, have developed large-scale cannabis cultivation methods that produce consistent, research-grade CBD and other cannabinoid chemotypes for clinical research.

Read this if you're interested in how cannabis is grown to pharmaceutical standards for clinical trials.

8 cannabinoid-dominant chemotypes developed by GW Pharmaceuticals for clinical research

What the researchers found

The review described the production practices of two institutions with extensive cannabis cultivation experience. GW Pharmaceuticals has developed a collection of cannabis chemotypes dominant in any one of eight different cannabinoids, with CBD and cannabidivarin (CBDV) chemotypes supporting epilepsy clinical trials.

The University of Mississippi, which holds the only federal license for cannabis research in the US, has established a germplasm bank of high-THC, high-CBD, and intermediate varieties. They developed an in vitro propagation protocol that produced cannabis clones with no detectable variations in morphology, physiology, biochemistry, or genetics compared to mother plants.

Both institutions covered breeding strategies, indoor and outdoor growing methods, harvesting protocols, and extraction techniques necessary for producing cannabis material that meets clinical trial standards.

Why it matters

Clinical research on cannabinoids requires standardized, consistent plant material. As CBD-based medicines advance through clinical trials (particularly for epilepsy), the ability to produce reliable chemotypes at scale becomes critical. This review documents the state of the art in medical-grade cannabis production.

The numbers in context

GW Pharmaceuticals: 8 cannabinoid-dominant chemotypes, 2 (CBD, CBDV) supporting epilepsy trials. University of Mississippi: germplasm bank of high-THC, high-CBD, and intermediate varieties. In vitro clones showed no detectable genetic or biochemical variation from mother plants.

How the study worked

Descriptive review of cultivation and production practices at GW Pharmaceuticals and the University of Mississippi. The review covered breeding, growing (indoor and outdoor), harvesting, and extraction methods used to produce research-grade cannabis.

What this study cannot tell us

Descriptive review of two specific institutions; not generalizable to all cannabis production. Details on yield optimization and production efficiency were limited. The review did not address cost, scalability challenges, or quality control standards for international markets.

How to read the evidence

Descriptive review of production practices at two leading institutions. Provides practical information but is not a clinical study.

When this study was published

Published in 2017. Cannabis cultivation science has advanced significantly since, with more institutions and countries engaged in research-grade production.

The bigger picture

The gap between recreational cannabis and medical-grade cannabis is vast. Clinical trials require exact cannabinoid profiles, absence of contaminants, and batch-to-batch consistency. As more cannabinoid-based medicines move toward approval, these production standards will define whether the field can deliver reliable treatments at scale.

Questions still open

  • Can these production methods be standardized across the growing number of research institutions? How do indoor versus outdoor growing methods affect cannabinoid profiles? Will genetic engineering eventually replace traditional breeding for medical cannabis?

Common questions

Why can't researchers just use regular cannabis?
Clinical trials require exact cannabinoid profiles, consistent potency, and freedom from contaminants. Street or dispensary cannabis varies wildly in composition. Medical-grade cannabis is grown from genetically characterized clones with standardized growing and extraction processes to ensure every batch is identical.
What is a cannabis chemotype?
A chemotype is a genetically distinct variety of cannabis that produces a specific dominant cannabinoid. While most recreational cannabis is high-THC, researchers have bred chemotypes dominant in CBD, CBDV, and six other cannabinoids to support research on specific therapeutic applications.

Read the original research

Cannabis cultivation: Methodological issues for obtaining medical-grade product.

Epilepsy & behavior : E&B, 70(Pt B), 302-312

Citation

Chandra, Suman; Lata, Hemant; ElSohly, Mahmoud A; Walker, Larry A; Potter, David. (2017). Cannabis cultivation: Methodological issues for obtaining medical-grade product.. Epilepsy & behavior : E&B, 70(Pt B), 302-312. https://doi.org/10.1016/j.yebeh.2016.11.029

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