Click me to open the menu
Click me to close the menu

Synthetic Cannabinoids

Synthetic cannabinoids (often called Spice) are highly potent, dangerous new psychoactive substances (former 'legal highs'). They are synthesised in a laboratory, sprayed onto plant material and then smoked. These drugs are highly dangerous, bear next to no relation to herbal cannabis and are linked to hundreds of deaths, particularly in prisons and on the streets. They were banned under the Psychoactive Substances Act 2016 and subsequently moved into Class B in their own right. Criminalising the drug has done little/nothing to stem its supply and has only served to further stigmatise and marginalise its vulnerable users.

What is synthetic cannabis?

“Synthetic cannabis” is a common, but misleading, term that refers to a class of substances more accurately called cannabinoid receptor agonists or synthetic cannabinoids. Whereas cannabis usually refers to the dried flowered buds of the actual plant, which derives its main psychoactive effect through THC, synthetic cannabinoids get their name from their action on various cannabinoid receptors in the brain.

Sacrificing accuracy for simplicity, people in public office, the media, and law enforcement use the term “synthetic cannabis” or the brand names of products sold, such as “Spice” or “K2,” that are known to contain various synthetic cannabinoids. “Spice” is now widely used to mean any and all synthetic cannabinoids, rather than any individual compound.

Many of these substances have different chemical structures than THC, the main psychoactive ingredient in cannabis, and bind very much stronger (10-80 fold) than THC to receptors in the brain. This means that they can produce very different effects than THC and is one possible reason for the higher rates of some of the more extreme side effects that are only occasionally seen in adverse reactions to cannabis.

Why do people use synthetic cannabinoid products like “Spice”

The emergence of synthetic cannabinoids has mirrored the same trends seen with other new psychoactive substances. Due to the ongoing prohibition of cannabis, emergence of the synthetic cannabinoid market over the last decade has met demand by being a legal or quasi legal alternative. Consequently – users could avoid possession charges and pass drug tests, particularly in prisons/on parole and in the workplace. Secondly, new psychoactive substances, as they were legal, were considerably cheaper than their illicit alternatives.

As people found many of the side effects strong and unpleasant, the use of synthetic cannabinoids decreased in the general population. Two key populations remain – prisoners and the homeless. As mentioned, synthetic cannabinoids are a) highly potent and b) hard to detect. Accordingly, they are ideal for smuggling into prisons, where supply is scarce. The high potency also accounts for the high incidence of use in the homeless – they produce a profoundly dissociating and depersonalising experience which helps insulate the user from the cold, harsh, and unpleasant environment of being on the streets.

What’s the difference between synthetic cannabinoids and cannabis?

Cannabis is a natural plant that grows both in the wild and is cultivated for its medicinal properties and for recreational use. Though synthetic cannabinoids are considered chemical relatives or analogues to substances in cannabis, they are not actually found in plant-based cannabis and therefore have chemical and pharmacological properties largely unknown outside of the laboratory.

What are the effects of synthetic cannabinoids?

Synthetic cannabinoids are mistakenly considered to closely mimic the effects of cannabis, but in fact there are significant differences. As their name suggests, synthetic cannabinoids, like THC and other substances in cannabis, affect the brain by stimulating activity at various cannabinoid receptors.

Although research is limited, preliminary studies suggest that positive effects include:

  • Feeling stimulated and energetic;
  • Increased appetite;
  • Producing a dream-like state,

Negative effects include:

  • Overdose and temporary psychotic states and unpredictable behaviours;
  • Sudden increase in body temperature, heart rate, coma and risk to internal organs (PMA);
  • Hallucination and vomiting;
  • Confusion leading to aggression and violence;
  • Seizures
  • Respiratory failure
  • Intense comedown that can cause users to feel suicidal.

The severe side effects are likely due to two key reasons:

  • Very high potency & strong binding to receptors in the brain;
  • An absence of naturally occurring cannabinoids found in herbal cannabis (like cannabidiol/CBD) which normally counteract the effects of THC.
How risky are synthetic cannabinoid products compared to cannabis or other drugs?

These substances are generally much more harmful than plant-based cannabis. Many of the adverse reactions to synthetic cannabinoids have been reported to involve dangerous, lethal physical symptoms. These include seizures, aggression and agitation, as well as respiratory failure and loss of consciousness. Adverse reactions to natural cannabis typically involve symptoms resembling anxiety and panic, which though worrisome, are not lethal.

Are there health conditions that make synthetic cannabinoids more dangerous?

Yes. Synthetic cannabinoids are pro-psychotic, and individuals with a history or family history of psychosis and mental health conditions are at elevated risk. They are also pro-convulsant, and individuals with a history or family history of epilepsy and other seizure disorders are at elevated risk.

What are the long-term risks and how addictive are synthetic cannabinoids?

Very little is known. A 2013 survey by the Scottish Drug Foundation found:

  • Increase in mental health issues including psychosis, paranoia, anxiety, ‘psychiatric complications’;
  • Depression;
  • Physical and psychological dependency happening quite rapidly after a relatively short intense period of use (weeks).
Myths and misunderstandings

A synthetic cannabinoid is cannabis made in a laboratory

Synthetic cannabinoids and the active psychoactive ingredient in cannabis, THC, are very different drugs. They bring about serious, life threatening side effects and are only linked to cannabis in that they bind to the same receptor in the brain as THC.


  • DrugScience
  • 2 Langley Lane
  • London
  • SW8 1GB
  • info@drugscience.org.uk