These chemicals are dissolved in solvents and sprayed onto dried plant material (often edible herbs that are otherwise inert and have no psychoactive effect of their own), so the finished product visually resembles cannabis and can be smoked in a similar way. It's sold under dozens of brand names — Spice, K2, Black Mamba, Scooby Snax, among many others — usually in eye-catching, brightly colored packaging, sometimes labeled "bath salts," "incense," or "not for human consumption" specifically to dodge drug legislation.

JWH-018 and the rest of the compounds in the "JWH series" take their name from the initials of Professor John W. Huffman, of Clemson University (United States). Huffman has explained that "we made that substance in 1995," as part of research published in 1998 in the Journal of Pharmacology & Experimental Therapeutics. JWH-018 is, literally, compound number 18 in a series of more than 470 THC analogs and metabolites that Huffman's team synthesized to study how they interact with the brain's cannabinoid receptors — pure basic research, with no intention whatsoever of creating a recreational drug.

THC (delta-9-tetrahydrocannabinol) is a partial agonist of the CB1 receptor — meaning it binds to the receptor and activates it, but only up to a point, with a natural biological "ceiling" that limits how much it can stimulate the receptor no matter how much the dose increases. Synthetic cannabinoids like JWH-018 (one of the most studied "Spice" compounds) bind to CB1 receptors with high affinity and stimulate G-proteins with an efficacy equal to or greater than THC's, and several of its metabolites produce full agonist levels of CB1 activation. A full agonist has no such "ceiling" — it drives the receptor to its maximum, without the natural brake that THC has. That molecular difference, seemingly technical, is ultimately why intoxication from synthetics is so different, so unpredictable, and so much more dangerous compared with cannabis.

Every bag of "Spice" can have a completely different concentration from the last one, even if bought from the same source the week before. A user who smoked a "safe" amount yesterday can smoke the same visual amount today and end up with an effective dose several times higher, simply because the chemical spraying onto the plant material is never even. With natural cannabis, the plant itself imposes biological limits on THC content; with synthetics, the only limit is however much chemical the manufacturer decided to use, with zero oversight.

"Spice" isn't a single compound — it's the street name for a diverse group of synthetic cannabinoid receptor agonists (SCRAs): lab-made drugs designed to mimic the effects of cannabis, but far more unpredictable and harmful. At a peak recorded in April 2017, the synthetic cannabinoid content in analyzed samples rose as high as 16%, triggering what the international press dubbed the "zombie epidemic": people collapsing in the middle of the street, frozen or moving erratically, for minutes or even hours at a time.

Unions and staff working in Spanish prisons have started using the term "cannibal drug" to describe a mixture of synthetic cannabinoids and other compounds soaked into sheets of paper — with no noticeable color or smell — that inmates smoke or inhale together with tobacco. One especially serious incident took place at Villahierro prison (León, Spain): within a few hours, five inmates ended up in critical condition at León Hospital after using these treated papers. In early 2026, similar patterns were reported at the prisons of Botafuegos and Puerto III (Cádiz, Spain), with impregnated sheets smuggled in through the mail, undetectable by the usual screening reagents, causing severe intoxication: loss of control, seizures, and states of extreme agitation.

A systematic review selected 21 studies covering a total of 55 patients with acute kidney injury induced by synthetic cannabinoids. Kidney damage was confirmed by elevated serum creatinine levels in 49 of those 49 evaluable patients (89%), and the most severe cases required hemodialysis. This is a type of damage that is essentially absent from the literature on natural cannabis intoxication — it's a direct consequence of the specific chemical toxicity of these synthetic compounds, not of the cannabinoid mechanism itself.

The most frequent withdrawal symptoms include psychosis, agitation/irritability, nausea/vomiting, seizures, tachycardia, and insomnia, along with mood swings, vivid dreams, tremor, chest pain, cramps, palpitations, breathing difficulty, cravings, headache, severe anxiety, loss of appetite, and excessive sweating. Onset of these symptoms can occur anywhere between 2 hours and a week after the last use, and severity appears to correlate with the amount of prior daily use.

Most standard urine drug tests, commonly used by employers or in workplace settings, don't detect synthetic cannabinoids, because traditional tests are designed to identify THC metabolites, not synthetic variants. When a drug's molecule doesn't match the target shape of the test's antibody, the result comes back negative — even if the substance is present in the body at dangerous levels. The structural novelty of these substances creates a direct mismatch with the antibodies built into standard panels.

In 2025, European countries identified 27 new cannabinoids, of which 16 were semi-synthetic cannabinoids, accounting for more than 50% of the new substances reported for the first time to the EU's Early Warning System. Law enforcement across EU member states reported a record amount of new psychoactive substances to the early warning system for the fifth year in a row, totaling 55 tonnes imported or seized. In 2025, 50 new psychoactive substances were reported for the first time — a clear sign of the ongoing challenge posed by clandestine manufacturers who keep designing new compounds to dodge existing legal controls.

Part of the problem is purely commercial: for years these substances were marketed as "legal highs," exploiting the fact that, as brand-new molecules, they weren't explicitly banned by law — until legislation caught up, at which point manufacturers would simply tweak the chemical structure slightly to create a technically different, and once again "legal," compound. This has absolutely nothing to do with legal CBD or with hemp flower under the legal THC threshold: they're completely different chemical families, with opposite safety profiles. Confusing "synthetic cannabis" with "a milder, legal form of cannabis" is probably the most dangerous misunderstanding in this entire subject.

• Seizures or uncontrollable muscle movements.
• Loss of consciousness or unresponsiveness.
• Difficulty breathing or very slow/shallow breathing.
• Chest pain or a sustained, very fast or irregular heart rate.
• Extreme agitation, aggression, or acute psychosis (delusions, intense hallucinations).
• Persistent vomiting, inability to keep fluids down, or signs of severe dehydration.
• No urine output or intense lower back pain (a possible sign of acute kidney damage).

Unlike with cannabis, where most bad experiences resolve on their own with time and a calm environment, intoxication from synthetics can rapidly turn into a genuine medical emergency. When in doubt, call emergency services — don't wait to see if it gets better.

This article is for informational and harm-reduction purposes only, based on published scientific and toxicological literature. It doesn't replace evaluation by a medical professional. If you or someone around you has used, or is suspected to have used, synthetic cannabis and shows any concerning symptoms, seek emergency medical care immediately — this is a potentially serious situation, not a mild intoxication comparable to cannabis.