Synthetic cannabinoids: what they are, why they are dangerous and how to recognize them
Synthetic cannabinoids (Spice, K2) are more dangerous than natural THC. Learn the symptoms of poisoning, first aid rules, and how to distinguish them from legal CBD material.
In Europe, over 900 new psychoactive substances have been reported since 2008, with synthetic cannabinoids being the largest and fastest-growing group (EMCDDA, Drug Profile 2023). Behind catchy names like Spice, K2 or “herbal incense” are chemical substances sprayed on plant material. They are not “weaker marijuana”. They are full agonists of CB1 receptors, acting many times stronger than natural THC, with no quality control or predictable dosage. Effects can be unpredictable even for experienced users, as the composition of the next batch changes without warning. This article explains the mechanism of danger, describes the symptoms of poisoning and first aid, and shows how to distinguish these substances from legal hemp material.
KEY INFORMATION
• Since 2008, the EMCDDA has recorded over 900 new psychoactive substances in Europe, with synthetic cannabinoids being the largest category (EMCDDA, Drug Profile 2023).
• Synthetic cannabinoids are full agonists of CB1, while THC is only a partial one, which explains their significantly greater toxicity.
• In case of suspected poisoning: call 112, place the person in the recovery position, do not leave them alone.
• Legal dried CBD hemp has a tested composition and contains less than 0.3% THC.
What are synthetic cannabinoids and where did they come from?
Synthetic cannabinoids are a broad group of chemical substances that bind to the same endocannabinoid receptors as THC. The first ones were synthesized in academic laboratories in the 1980s and 1990s for research on the endocannabinoid system (EMCDDA, Drug Profile 2023). No one planned to sell them as recreational drugs at that time.
They appeared on the market after 2004, when chemists began applying these compounds to plant material and selling it as “incense herbal blends”. This gave the products a seemingly legal character, as the substances used were not yet included in drug laws. In Poland, the legal highs market flourished particularly intensively between 2008 and 2010. A complete overview of the mechanism of action and history of these substances can be found in our comprehensive guide to synthetic cannabinoids.
We noticed in available reports something that eludes most popular science articles: the problem with synthetic cannabinoids is not that one substance is “bad”. Every year, dozens of new analogs appear, designed to circumvent the current list of banned substances. It is a legislative race that users have no chance of winning.
Why are synthetic cannabinoids more dangerous than natural marijuana?
The key difference lies in the type of binding to the CB1 receptor. Natural THC is a partial agonist of the CB1 receptor, so it only partially activates it, which biologically limits the intensity of effects. Synthetic cannabinoids, on the other hand, are full agonists: they bind to the receptor and activate it maximally (Fantegrossi et al., Life Sciences, 2014). This is the fundamental mechanism of their greater toxicity.
In the natural cannabis plant, THC coexists with CBD and dozens of other phytochemicals. CBD acts as a partial antagonist of CB1, mitigating the effects of THC. In synthetic Spice products, there is no such buffer. You get pure, maximum stimulation of the CB1 receptor. The differences between phytocannabinoids, endocannabinoids produced by the body, and synthetic compounds are detailed in a separate tabular comparison.
The third difference is the lack of dosage control. The substance is sprayed unevenly on the material. One batch may contain concentrations a hundred times higher than a neighboring one. The user has no way to predict how much substance they have taken. This explains why sudden hospitalizations occur even among those with “experience” with these products.
What symptoms does poisoning with synthetic cannabinoids cause?
Symptoms of poisoning with synthetic cannabinoids appear quickly, usually within a few to several minutes of exposure. A review of nearly 4000 clinical cases published in the journal Clinical Toxicology indicates that the most common single symptom is tachycardia (in about 37-77% of patients), while rarer but serious complications include stroke, heart attack, acute kidney injury, tonic-clonic seizures, and psychotic episodes (Tait et al., Clinical Toxicology, 2016). The table below collects warning signals in one place.
| Symptom / warning signal | Health risk | What to do immediately |
|---|---|---|
| Tachycardia, palpitations, arrhythmia | Heart attack, sudden cardiac arrest | Call 112, do not let the person stand up |
| Psychosis, hallucinations, severe anxiety, paranoia | Permanent mental disorders, risk of self-harm | Speak calmly, remove dangerous objects, call 112 |
| Seizures | Head injury, asphyxia, metabolic acidosis | Protect the head, do not put anything in the mouth, call 112 |
| Loss of consciousness | Aspiration of vomit, brain hypoxia | Place in the recovery position, do not leave alone, call 112 |
| Severe aggression or extreme agitation | Injuries, rhabdomyolysis, hyperventilation | Do not restrain physically, keep your distance, call 112 |
| Hypothermia or hyperthermia (extreme body temperatures) | Organ damage, shock | Cover or cool depending on the symptom, call 112 |
| Vomiting, severe abdominal pain, pallor | Aspiration, dehydration, toxic kidney damage | Place on the side, do not give anything orally, call 112 |
Call 112 for any of the above symptoms. Do not leave the person alone, even if they seem to be regaining contact with reality: their condition can deteriorate rapidly.
How to recognize synthetic cannabinoids?
EMCDDA points out several characteristic visual and packaging features that distinguish Spice products from legal hemp material. Knowledge of these signals can save lives, as the external appearance is often the only available information before use (EMCDDA, Drug Profile 2023). The following comparison shows the differences side by side.
| Feature | Legal CBD hemp material | Spice / K2 product (legal high) |
|---|---|---|
| Packaging and label | Clear label with name, cannabinoid content, and manufacturer details | Colorful foil packaging, often with the note ‘not for human consumption’ - this is a legal trick that does not make the product safer |
| Appearance and smell of the material | Visible trichomes, i.e., silvery resin crystals, and a strong terpene aroma | Uniform color, lack of trichomes, chemical smell, sweetish or none |
| Composition and certificates | Defined cannabinoid profile, laboratory test results available publicly | No list of active substances or only a general description ‘herbal blend’ |
Our observations indicate that many people buying legal highs never check the composition, as there is no list of active substances on the packaging. Legal cannabis products have a defined cannabinoid profile with laboratory tests available on request or published on the manufacturer’s website. The lack of verification of the composition is the number one warning signal. If you have doubts about the composition of the substance you possess, in some countries in Europe, drug-checking services operate, which we have described separately drug-checking, which we have described separately.
Legal aspects: are “legal highs” legal in Poland?
It is worth knowing that synthetic cannabinoids themselves are not a homogeneous group. The EMCDDA has cataloged over 200 different compounds classified in this category. Each may have a different toxicity profile, different dosing window, and different duration of action. A person who has “survived” one product without serious effects has no guarantee that the next batch, even sold under the same name, will behave the same way. The composition changes without notifying the consumer.
The Act on Counteracting Drug Addiction provides a fast track for entering new psychoactive substances on the list: the Minister of Health can do this by regulation, without waiting for the full legislative procedure. This happened, for example, with HHC, which was moved to group II-P of psychotropic substances by regulation on July 7, 2026 (HHC is another semi-synthetic compound, which we discuss separately in the guide to HHC products - do not confuse it with the fully synthetic cannabinoids like Spice described here). Nevertheless, Spice manufacturers regularly modify the chemical molecule, introducing another analog that is not yet formally on the list.
Possession of substances from the list of new psychoactive substances is sanctioned administratively or criminally, depending on the quantity and circumstances. Trading in such substances is a crime punishable by imprisonment, harsher when acting for profit or against minors. The fact that a specific molecule is not yet on the list does not protect against criminal liability for trading it.
Legal dried hemp as a transparent alternative
Legal industrial hemp is subject to strictly defined standards: the allowable THC content, calculated as the sum of delta-9-THC and THCA, must not exceed 0.3% dry weight (art. 4 point 5 of the Act on Counteracting Drug Addiction, Dz.U. 2022 item 763). The same numerical threshold applies in EU agricultural subsidies for hemp varieties eligible for support under the Common Agricultural Policy (Regulation (EU) 2021/2115). This is a completely different class of product than Spice.
The difference is not just in legality. Legal hemp contains natural phytochemicals and terpenes in the proportions produced by the plant. The composition is known and verifiable. There is no risk that one gram contains a dose ten times higher than the previous one. This predictability is a fundamental safety advantage. Legally operating sellers are subject to quality control and must be able to demonstrate the origin of the raw material, which eliminates the risk of accidental contact with an unknown chemical substance. This significantly reduces the likelihood of experiencing symptoms described earlier, such as tachycardia or seizures, when using products from a legal source.
Frequently asked questions
What are synthetic cannabinoids and why are they used?
Synthetic cannabinoids are chemical substances sprayed on plant material and sold under names like Spice, K2 or legal highs. They act on the same CB1 receptors as natural THC, but with many times greater potency. They are used because they are cheap and difficult to detect in standard drug tests (EMCDDA, Drug Profile 2023).
Why are synthetic cannabinoids more dangerous than natural marijuana?
Synthetic cannabinoids are full agonists of CB1 receptors: they bind to them more strongly than THC and fully activate them. THC is a partial agonist, which limits its toxicity. Synthetic products also lack natural CBD, which partially mitigates the effects of THC in the plant (Fantegrossi et al., Life Sciences, 2014).
What to do if someone loses consciousness after using synthetic cannabinoids?
Immediately call 112. Do not leave the person alone. Place them in the recovery position to prevent choking on vomit. Do not give any substances or medications. Rescuers need to know what was taken, so provide this information to the emergency dispatcher.
How to recognize synthetic cannabinoids on a label or packaging?
Look for the warning ‘not for human consumption’ or ‘not intended for human consumption’. The packaging often resembles a herbal mixture with colorful graphics. The material does not have visible trichomes or the characteristic smell of cannabis. It is often uniformly green or has a strange, chemical aroma (EMCDDA, Drug Profile 2023).
Are legal dried CBD hemp flowers a safe alternative to legal highs?
Legal dried CBD hemp from certified European farms has a tested, transparent composition. It contains less than 0.3% THC, calculated as the sum of delta-9-THC and THCA, and does not contain synthetic compounds. It is a completely different product: regulated, quality-controlled, free from unpredictable chemical substances that make Spice so dangerous (art. 4 point 5 of the Act on Counteracting Drug Addiction, Dz.U. 2022 item 763).
If you care about a product with a predictable, tested composition instead of a lottery with an unknown chemical substance, check the offer of legal hemp material in our store.
This article is for informational and educational purposes only and does not constitute legal advice. The legal status described in the article is valid as of the date of publication: regulations regarding cannabis may change. Before making a decision, consult a lawyer or current legal acts.
Author: Michał Waluk · Published: 2026-08-09 · Updated: 2026-08-10
