Ask Dr. Leigh: When it comes to medical cannabis, do strains matter?

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Using cannabis can have a big impact on your physical and mental health—for better, and sometimes for worse. That’s why it’s important to consult a healthcare provider before experimenting.

Here at GreenState, cannabis clinician Dr. Leigh Vinocur is here to answer your questions on healthy living with cannabis.

Editor’s Note: The answer to this question is meant to supplement, not replace, advice, diagnoses, and treatment from a healthcare provider.  Always consult a medical professional when using cannabis for medicinal purposes, and do not disregard the advice of your healthcare provider because of anything you may read in this article. 

Q: When it comes to medical cannabis, do strains matter?

A: This is an interesting question because I often hear from my patients that the dispensary staff are pushing specific strains for certain medical problems. But scientifically speaking, I don’t believe it is that simple and we probably have not advanced the science to that point yet. Today the most precise way to classify cannabis, especially for medical use, is based on the chemical characteristics of the cannabinoids themselves. And in a prior article that I contributed to GreenState, I discussed how modern genetic testing has shown strain inconsistencies and really while there were 2 genetic subtypes these did not correspond to Sativa, Indica or hybrids, nor the names these strains that we see in dispensaries today.

Remember it wasn’t until the 1960s, when Dr. Raphael Mechoulam discovered THC, that we even knew what the chemical compounds in cannabis were. Prior to our modern era the classification and taxonomy (naming) of cannabis had been quite a controversial debate since the 18th century when Swedish botanist Carl Linnaeus named Cannabis sativa L proclaiming it a single species, while Jean-Baptiste Lamarck, the father of evolutionary biology,  described a strain from India, which he claimed was a second species C. indica Lam.  Obviously back in that time, biologists and botanist had only morphologic features, called phenotypes in genetics, to go by when classifying these plants, meaning the outer characteristics such as the shape of the leaves or the height of the plant.

Sativa had narrow pointy leaves with no pattern on them, described as lighter green and was taller and slender reaching up to 8-12 feet in height.  Whereas, Indica had broad roundish dark blue-green leaves with a marble-like pattern on them as well as being a bushier shorter plant usually not more than 3-6 feet in height.  But even in the 18th century Lamarck noted Indica when consumed, seemed to have greater intoxicating effects when compared with Sativa.

Complicating matters even more, is the fact that cannabis is one of the oldest cultivated plants that humans have used for food, fiber and medicine, some accounts dating back 5000 years.  That means that early man may have had a hand inadvertently causing natural selection in wild population landraces, meaning the local cultivar, as they migrated throughout the globe, as well as modern man intentionally crossbreeding plants for desired cannabinoid traits today.  That is why today those morphologic distinctions especially between Sativa and Indica and their hybrids mean even less, as modern cannabis has been crossbred for many years now, mainly for its THC content.

As opposed to morphologic phenotypes, today’s hybrids are classified according to the chemical composition of their cannabinoids which are called chemotypes or chemovars.

Today we can use genomic mapping as well as chemometric analysis to classify strains of cannabis according to their cannabinoid content, which is much more meaningful for medical cannabis use.

Strains are now classified via a 3-tier chemotype system, ranking the cannabinoid constituents. Type I is THC-dominant with concentrations above 0.3% but many have been bred today to have up to 20-30% THC. Type II is considered intermediate with respect to THC.  It has a mixed ratio of THC to CBD, but industry standards usually start at a 1 to 1 ratio.  Type III is CBD-dominant, sometimes classified as hemp, the THC content is always less than 0.3%.  There is even classification beyond THC, Type IV is CBG-dominant which is a cannabinoid called cannabigerol, which is a minor cannabinoid that we are just learning more about its potential beneficial medical effects. And Type V is described as cannabinoid-null or -zero, this chemotype refers to cannabis plants that produce little to no cannabinoid content often used for its fiber.

Interestingly modern genomics used in this last decade has again brought about the idea of two distinct major gene pools, as opposed to the hypothesis of a single undivided cannabis species. Nevertheless, whether cannabis is made up of one species or two, using this tiered chemotype chemovar designation is more practical, more accurate and more precise a classification system when it comes to the medicinal use of cannabis.

However, complicating physician recommendations even further with these defined chemotypes is the fact that there are still so many different variations in these hybrid strains related to exact cannabinoid ratios, as well as other bioactive compounds such as their terpene and flavonoid profiles. Additionally, we still often lack consistent batch-to-batch standardizations of these cannabinoid medications.  However, today most physicians recommend cannabis based on its cannabinoid profile, such as THC-dominate versus CBD-dominant versus a 1 to 1 ratio.

While we are still learning more about the potential use of minor cannabinoids, flavonoids and terpene profiles medically, I tell my patients that in my opinion, despite what dispensary attendants might tell them, there is still not any clear-cut scientific evidence for recommending a specific strain to treat a specific medical disease.


Got cannabis questions? Ask Doctor Leigh. Send your questions to GreenState’s Assistant Editor Elissa Esher at and keep an eye out for new answers from Dr. Leigh Vinocur every month.

Dr. Leigh Vinocur is a board-certified emergency physician who also has a cannabis consulting practice for patients and industry. She is a member of the Society of Cannabis Clinicians and a graduate of the inaugural class, with the first Master of Science in the country in Medical Cannabis Science and Therapeutics from the University of Maryland School of Pharmacy.

For more advice from Dr. Leigh and other cannabis-informed healthcare professionals Dr. Leslie Matthews and Dr. Hal Altman, listen to “Cannabis Grand Rounds” here: 

The response to this question was not written or edited by Hearst. The authors are solely responsible for the content.

Leigh Vinocur, MD