Genetic analysis of 30 commercially available cannabis strains found no clear genetic distinction between sativa, indica, and hybrid types, and significant genetic inconsistencies within strains from different dispensaries.
Cannabis consumers, dispensary operators, regulators, and medical cannabis patients who rely on strain-specific effects.
Sativa/indica labels had no genetic basis
The Backstory
Walk into a dispensary in Denver and buy a gram of Sour Diesel. Fly to Seattle and buy Sour Diesel from a shop there. Drive to Los Angeles and buy it again. You have three products with the same name, from three legal markets, presumably the same strain.
Anna Schwabe ran the DNA. They were not the same plant.
In 2019, Schwabe and Mitchell McGlaughlin from the University of Northern Colorado published the first genetic study to directly test whether cannabis strain names mean what consumers think they mean. They purchased 122 samples of 30 strains from 20 dispensaries across Colorado, California, and Washington, developed new genetic markers, and asked the simplest possible question: when two shops sell "Blue Dream," are they selling the same thing?
The answer, for many strains, was no.
Why Nobody Had Tested This Before
Cannabis occupies a unique regulatory void. Unlike virtually every other commercially grown plant in the United States, it is excluded from USDA regulation. Distinctive cannabis varieties cannot be registered through the standard Plant Variety Protection system. There is no national catalog of verified genetic identities for cannabis strains, no certification body, and no verification requirement.
For every other crop — tomatoes, apples, wheat, roses — the agricultural system includes formal variety registration, breeder's rights protections, and genetic verification. If you buy a Honeycrisp apple tree, it is genetically a Honeycrisp apple tree. The system enforces this.
Cannabis has none of that infrastructure. Strain names are assigned by growers, inherited through clonal propagation and seed trading, and passed along through an underground market that predates legalization by decades. There was never a catalog, never a registry, and once the legal market opened, no one built one. Schwabe and McGlaughlin decided to test what that absence had produced.
The Methodology
How They Did It
How They Tested Strain Consistency
Develop genetic markers
Created 10 new microsatellite markers using the published Purple Kush genome as a reference. Microsatellites are short, repeating DNA sequences that vary between individuals — like genetic fingerprints.
De novo marker development was necessary because standardized cannabis genetic markers did not exist
Sample collection
Purchased 122 cannabis samples representing 30 named strains from 20 licensed dispensaries across Colorado, California, and Washington.
Multiple samples of the same strain from different facilities — the key test of consistency
Genetic fingerprinting
Extracted DNA from each sample and amplified the 10 microsatellite loci. Compared the resulting genetic fingerprints within strains (same name, different source) and between strains (different names).
Standard population genetics methodology adapted for cannabis
Statistical analysis
Used STRUCTURE analysis and principal coordinates analysis to identify genetic clusters. Tested whether clusters corresponded to reported sativa/indica/hybrid classifications.
Two statistically robust genetic groups emerged — but they did not match sativa/indica/hybrid labels
Schwabe & McGlaughlin (2019), J Cannabis Research 1(1):3
What They Found
The results tell two stories — one alarming, one partially reassuring.
The Alarming Finding
strong- Most strains contained at least one genetic outlier — a sample that was genetically distinct from other samples sold under the same name
- Two samples both sold as 'Sour Diesel' were less genetically similar to each other than samples sold under completely different names ('Golden Goat' and 'Island Sweet Skunk')
- 'Larry OG' and 'Tahoe OG' — marketed as distinct strains — were genetically identical
- The two genetic groups identified by STRUCTURE analysis did NOT correspond to sativa, indica, or hybrid categories
- Strain inconsistency was not limited to a single source — it existed across dispensaries, cities, and states
The Partially Reassuring Finding
moderate- After removing obvious outliers, many strains showed considerable genetic stability
- Some strains (like Blue Dream, with 89% similarity across 9 samples) maintained reasonable consistency
- The problem appears to be inconsistent naming and propagation practices, not total genetic chaos
- Within a single grower or dispensary chain, strain names are likely more reliable than across the industry
- The genetic tools developed in this study could form the basis of a future verification system
Schwabe & McGlaughlin (2019), J Cannabis Research 1(1):3
2,000+
named cannabis strains are commercially available, but no standardized genetic verification system exists. This study tested 30 — fewer than 2% — and found widespread inconsistency. When 'Golden Goat' from one dispensary is more genetically similar to 'Island Sweet Skunk' than to another shop's 'Golden Goat,' the naming system is functionally broken for cross-source comparisons.
Compare this to wine, where appellation systems, grape variety registries, and regulatory oversight mean that a bottle labeled 'Pinot Noir' from any producer will actually contain Pinot Noir grapes. Cannabis has no equivalent.
Schwabe & McGlaughlin (2019)
Why This Matters for Consumers
For recreational users, strain inconsistency means unexpected experiences. You tried Blue Dream once, liked it, and bought it again from a different shop — but the genetics are different, the terpene profile is different, and the experience is different. Annoying, but manageable.
For medical patients, the implications are more serious. Patients who find a strain that reliably alleviates specific symptoms — chronic pain, insomnia, nausea — depend on consistency. If the "Harlequin" they buy this month is genetically unrelated to the "Harlequin" that worked last month, their treatment becomes unpredictable.
The Bigger Picture: No Verification System
Schwabe's study didn't just document a problem — it highlighted a structural absence. Every other legal agricultural product in the United States has some form of variety verification. Cannabis, because of its federal scheduling and the speed with which state-level legalization outpaced regulatory infrastructure, has none.
The result is a naming system that evolved from underground culture, was adopted wholesale by the legal market, and has never been scientifically validated. Strain names carry cultural meaning, marketing value, and consumer expectations — but they do not carry genetic guarantees.
This finding connects directly to Piomelli and Russo's 2016 argument that the indica/sativa framework is "total nonsense." Schwabe's data shows it is worse than that: even within the strain-name system, consistency is not assured. The indica/sativa labels are unreliable, and the strain names within those categories are also unreliable.
The Watts et al. 2021 study in Nature Plants later confirmed Schwabe's findings with an even larger genomic dataset: sativa and indica labels are genetically indistinct on a genome-wide scale, with the only consistent association being terpene synthase genes that influence aroma — the labels track smell, not pharmacology.
Myth vs. Reality
If I buy the same strain name from any dispensary, I'm getting the same product.
Genetic analysis of 30 strains across 20 dispensaries in three states found that most strains contained at least one genetic outlier. Two samples of 'Sour Diesel' from different sources were less genetically similar than samples of 'Golden Goat' and 'Island Sweet Skunk.' Strain names are reasonably reliable within a single grower but unreliable across the industry.
The Evidence
Schwabe & McGlaughlin (2019): 122 samples, 30 strains, 20 dispensaries, Colorado/California/Washington. De novo microsatellite marker analysis.
Schwabe & McGlaughlin (2019), J Cannabis Research 1(1):3
If I can't trust strain names, how should I choose cannabis?
Look at the lab testing results, not the name. The cannabinoid profile (THC percentage, CBD percentage) and terpene profile tell you more about what a product will do than the strain name. If you find a product that works for you, buy it from the same source — strain names are more reliable within a single grower than across the industry. Our dispensary guide explains how to read lab results.
Are any strain names reliable?
Yes — some strains showed considerable genetic stability even across different sources. The study found that after removing obvious outliers, many strains maintained genetic consistency. Strains propagated through cloning (rather than seeds) tend to be more genetically stable. Major, well-established strains from reputable breeders are more likely to be consistent than obscure or newly named varieties.
Why doesn't the government regulate cannabis strain names?
Cannabis is excluded from USDA regulation and cannot be registered through the Plant Variety Protection system because of federal scheduling. State-level legalization has moved faster than regulatory infrastructure. Some states are developing testing and labeling requirements, but no standardized national genetic verification system exists for cannabis varieties.
Does this mean all dispensary products are unreliable?
No — but it means strain names should not be your primary decision-making tool. The lab testing data (required in most legal states) tells you what is actually in the product. Reputable dispensaries that maintain good supply chain relationships with specific growers are more likely to offer consistent products. The naming system is a convenient shorthand, not a quality guarantee.
Related Research
The Science of Cannabis Labeling and Classification
Schwabe's genetic work is part of a growing body of evidence showing that the cannabis industry's classification and naming systems need fundamental reform.
The Cannabis sativa versus Cannabis indica debate: an interview with Ethan Russo, MD
Piomelli & Russo (2016)
The expert argument that sativa/indica labels are 'total nonsense' — Schwabe's data proved it genetically
Taming THC: potential cannabis synergy and phytocannabinoid-terpenoid entourage effects
Russo (2011)
The entourage effect review — if terpene and cannabinoid profiles matter more than strain names, then chemical testing is essential
Terpenes/terpenoids in cannabis: are they important?
Hanuš & Hod (2020)
Analytical chemistry of 108 cannabis chemotypes — the kind of chemical fingerprinting that should replace unreliable strain names
Cannabis and the anxiety of fragmentation: biphasic effects
Crippa et al. (2009)
When strain names are unreliable, the biphasic dose-response curve becomes even more important — start low because you don't know exactly what you're getting
What the researchers found
Using 10 microsatellite markers, researchers found two genetic groups, but these did not correspond to sativa/indica/hybrid labels. Most strains had at least one genetic outlier, meaning the same strain name from different dispensaries could be genetically different. After removing outliers, many strains showed considerable stability.
Why it matters
Millions of consumers choose products based on sativa/indica labels, believing they predict effects. This study shows those labels have no genetic foundation, meaning consumers may be making decisions based on unreliable information.
The numbers in context
30 strains tested from dispensaries in 3 states. 10 microsatellite markers used. 2 genetic groups found, but neither corresponded to sativa/indica/hybrid labels. Most strains had at least 1 genetic outlier.
How the study worked
Developed 10 de-novo microsatellite markers from the Purple Kush genome. Tested 30 commercially available drug-type cannabis strains obtained from dispensaries in three US states.
Who was studied
122 samples of 30 cannabis strains purchased from 20 dispensaries in Colorado, California, and Washington
What this study cannot tell us
Limited to 30 strains. Microsatellite markers capture only part of genetic variation. Chemical profiles (cannabinoid and terpene content) were not measured and may be more relevant to effects than overall genetic identity.
How to read the evidence
Moderate: rigorous genetic methodology applied to a meaningful sample, but limited strain number.
When this study was published
Published in 2019.
The bigger picture
For recreational users, genetic inconsistency means unexpected effects. For medical patients relying on specific strains for symptom relief, it means potentially receiving a different product than intended, which could have serious consequences.
Questions still open
- Should the cannabis industry move to chemotype-based labeling instead of sativa/indica? Would standardized genetic testing at dispensaries improve product consistency? How much phenotypic variation exists within genetically similar plants?
Common questions
Does this mean sativa and indica don't exist?
How should consumers choose cannabis products?
Read the original research
Genetic tools weed out misconceptions of strain reliability in Cannabis sativa: implications for a budding industry.
Journal of cannabis research, 1(1), 3
The first journal dedicated to cannabis research — published in its inaugural volume, establishing genetic verification as a priority for the nascent legal industry.
Citation
Schwabe, Anna L; McGlaughlin, Mitchell E. (2019). Genetic tools weed out misconceptions of strain reliability in Cannabis sativa: implications for a budding industry.. Journal of cannabis research, 1(1), 3. https://doi.org/10.1186/s42238-019-0001-1
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