When “Cannabis” Is Not the Whole Story: The Health Risk of Undeclared Synthetic Cannabinoids in Low-THC Flower

The European Union Drugs Agency’s 2026 reporting warns about increasing adulteration of low-THC cannabis and CBD products with synthetic cannabinoids. It also describes the continuing commercial availability of semi-synthetic cannabinoids, including low-THC cannabis that has been sprayed or mixed with these compounds.

For clinicians, consumers and responsible retailers, the key issue is not the terminology used on the packet. It is the possibility that a familiar-looking cannabis product contains an undeclared or poorly characterised pharmacologically active substance.

Synthetic and semi-synthetic cannabinoids should not be conflated

The first requirement is precise language.

Synthetic cannabinoid receptor agonists, often associated with products historically marketed as Spice, are laboratory-created compounds that act on cannabinoid receptors and can be highly potent.

Semi-synthetic cannabinoids are chemically modified forms of cannabinoids related to those found in cannabis. HHC is one widely recognised example, although the category now includes many other compounds.

These groups differ in chemistry, pharmacology and risk.

They also differ from naturally occurring delta-9 THC and non-intoxicating CBD.

Public-health messaging becomes less credible when all novel cannabinoids are described as the same thing. However, the opposite error is also problematic: treating a compound as low risk solely because it was made from CBD or marketed as hemp-derived.

Risk has to be assessed compound by compound and product by product.

A rapidly expanding market

The pace of cannabinoid emergence makes that difficult.

EUDA reports that European countries identified 27 new cannabinoids in 2025, 16 of them semi-synthetic. By the end of 2025, 40 semi-synthetic cannabinoids had been identified on European drug markets.

The agency says the effects of semi-synthetic cannabinoids in humans remain poorly studied. Reported adverse reactions range from mild effects to severe poisoning requiring hospital treatment, and concerns exist around psychotic episodes, abuse and dependence potential.

HHC was placed under international control in December 2025, but replacement compounds continued to appear.

This cycle creates a persistent evidence gap. Commercial availability can precede robust toxicological and clinical understanding.

Undeclared exposure changes the clinical picture

The public-health concern is greatest when a consumer does not know that another substance is present.

EUDA warns that potent synthetic cannabinoids may adulterate cannabis and semi-synthetic cannabinoid products without consumers’ knowledge.

In September 2025, Czechia reported a poisoning outbreak linked to MDMB-PINACA sold in “legal high” type products.

The UK Advisory Council on the Misuse of Drugs has documented a broad range of adverse effects associated with synthetic cannabinoid receptor agonists. These include loss of consciousness, sometimes with respiratory depression, rapid heart rate, nausea and vomiting, agitation, confusion, behavioural disturbance, psychosis and seizures. More severe reported effects include cardiac dysrhythmias, cardiac arrest, myocardial infarction, stroke and acute kidney failure.

The ACMD has also noted that deaths involving these compounds may be underestimated because synthetic cannabinoid receptor agonists are not necessarily included in routine drug screens.

This has implications for clinical history-taking.

If a patient says they consumed “weed,” “CBD flower,” “legal weed” or “hemp,” the label may not identify the pharmacologically relevant exposure.

The flower format can mask the difference

Low-THC cannabis is an effective carrier for added compounds because it retains the appearance and aroma of cannabis.

There may be no reliable visual indication that the product was treated after harvest.

That makes consumer recognition difficult and places greater importance on labelling, retail disclosure and analytical testing.

The problem is not limited to deliberate deception. A retailer may itself misunderstand a wholesale product or rely on incomplete documentation.

A product can therefore pass through several hands while the distinction between base flower and added active compound becomes less clear.

Product variability adds another risk

EUDA reports that products and batches containing semi-synthetic cannabinoids can differ widely in the compounds and concentrations present, with some containing undeclared cannabinoids or high amounts.

This variability is relevant to both public health and clinical interpretation.

If an active compound is applied to plant material, uneven distribution may also make the consumer’s dose less predictable than a simple label value suggests.

A person who previously tolerated one portion of a product may therefore have a different experience with another portion or batch.

The evidence does not justify assuming that every infused flower is dangerously uneven. It does justify treating manufacturing consistency as a safety variable rather than a cosmetic quality issue.

Laboratory testing has limits

Certificates of analysis are useful only when their scope is understood.

A standard cannabinoid profile may measure expected natural cannabinoids. It does not necessarily screen for a novel semi-synthetic compound or synthetic cannabinoid receptor agonist.

Likewise, a certificate for base hemp flower does not describe a product that was subsequently infused.

For products intentionally treated after harvest, meaningful testing should focus on the finished product and clearly identify the analytical scope.

This is particularly important for clinicians and poison-information services because product labels and routine toxicology may not provide a complete exposure history.

Public health communication should avoid two extremes

The first extreme is minimisation: assuming that anything sold as hemp or CBD must carry the risk profile of CBD.

The second is sensationalism: describing every modified cannabinoid product as Spice.

Neither helps patients or consumers.

A more useful message is:

CBD itself is not the same as a potent synthetic cannabinoid receptor agonist.

Semi-synthetic cannabinoids are a diverse and evolving group with limited human evidence for many compounds.

Low-THC cannabis can be used as a carrier for substances added after harvest.

The finished product, not simply the plant material, determines exposure.

This framing protects both consumers and the credibility of health communication.

The role of responsible retail 

Although this is fundamentally a public-health issue, retail practice matters.

Businesses selling low-THC or cannabinoid products should be able to identify what was added, provide batch-specific finished-product testing, explain the analytical panel and label psychoactive additions clearly.

At Originals CBD, operating in the European CBD sector has reinforced the importance of separating conventional CBD products from products whose effects are created by added intoxicating compounds.

That distinction is important not only for brand reputation but for health surveillance.

If consumers, clinicians and laboratories are all using the broad term “CBD flower” for chemically different products, meaningful risk assessment becomes harder.

Europe’s evolving cannabinoid market requires better vocabulary, better testing and better disclosure.

The first step is recognising that when someone says they consumed cannabis, cannabis may not be the whole story.