On the 26th May 2016, the United Kingdom introduced a blanket ban on new psychoactive substances, widely described in the media as ‘legal highs’. Well, legal no more – under the Psychoactive Substances Act, production, distribution, or sale are now criminal offences. This is a troubling development for science-based policy and law enforcement.

What are, or rather were, legal highs? These are synthetic compounds that produce similar psychotropic effects to illegal drugs such as marijuana or cocaine, but have been designed to possess a different enough chemical structure to bypass existing UK legislation regulating their use and sale. They have seen increase popularity, with the UK being the largest market for legal highs in the EU. Crucially, their role in causing harm – potential for addiction, long-term health consequences and associated risks – is poorly understood.

Under the recently introduced legislation, such substances are now automatically illegal. The new Act defines them as:

“any substance which—

(a) is capable of producing a psychoactive effect in a person who consumes it, and (b) is not an exempted substance. […] a substance produces a psychoactive effect in a person if, by stimulating or depressing the person’s central nervous system, it affects the person’s mental functioning or emotional state.”

In summary, that is any substance that alters ‘mental functioning of emotional state’, and is not already regulated through some other legislation. This is a problematic definition, as it is far too broad to be useful, and it ignores the critical aspect that practitioners look for in drug legislation – the potential for causing harm. This contradiction manifests in two important ways: establishing whether a substance is psychoactive and the lack of evidence-based steering for legislation.

Establishing psychotropic status

Voices in law enforcement and the scientific community have already voiced their concerns, stating that such a ban is unenforceable. What do they mean by this? We first have to look at the way we define whether a substance produces a psychoactive effect. There is currently no predictive method to establish a causal relationship between the molecular structure of a substance, and their capacity to induce changes to cognition or emotion. The only route to ensure whether a given substance has a psychotropic effect is to conduct human clinical trials, querying the participant’s subject experience. Perversely, with the introduction of a blanket ban it is precisely this type of clinical trials that become difficult or impossible to conduct.

It is worth pointing out that, for example, coffee and alcohol would fall under this legislation, lest for the case that they are already regulated by existing laws. These are substances that as a society we consider as acceptable, either because their risk and health effects are considered mild enough (coffee), or because we accept a culture of consumption as a reasonable precedent, despite the fact that alcohol is far more dangerous than other regulated drugs.

Lack of evidence in legislation

The argument for the regulation of drugs is usually constructed around the concept of harm – harm to the self, due to addictive behaviour and long-term health risks, or harm to others, due to altered behaviour or financing of criminal drug enterprises. The troubling development in the UK courts is that we have little evidence on the risk of harm for most of the substances that fall under this new legislation.

While some of the substances tackled may indeed pose serious risk of harm, other may not, and this lack of evidence creates a scenario where individuals may be criminally prosecuted for dealing in a substance that has unproven capacity for harm. This is moving from evidence-based policy where the objective is harm reduction, to morality-based policy, stating that inducing altered cognitive or emotional states is inherently immoral and therefore illegal.

This approach is not good enough, for two reasons. First, because we live in a multicultural society where judgements based on plurality-defined morals and traditions cam exclude and stigmatise minorities, as we have already seen with the psychotropic khat and the Somali community. Second, the objective of such legislation should be first and foremost harm reduction, nor criminalising users. It is often the poor and vulnerable who are most at risk of both substance abuse and criminal convictions, creating a system for marginalisation of sectors of the population. As a society may decide this is acceptable in the name of harm reduction, when the evidence is available. When there is no evidence, such choices become even more difficult.

Then there is the question of criminality. One argument in favour of the bill is that it will force so-called ‘head shops’ to close, therefore reducing the legal loophole for providers of psychoactive substances. But critics have raised concerns that this will simply drive the supply underground, putting users in the hands of criminal gangs, and placing the narcotics trade even further away from the arm of the law. In addition, the past two decades of collective experience in substance abuse has shown that criminalisation is significantly less effective than clinical intervention in preventing narcotics trafficking and undermining the criminal enterprises that sustain it.

There is no question that unregulated substances may pose a significant risk to health, particularly amongst vulnerable users. But ultimately, it is the poor and disadvantaged who will likely suffer from the newly introduced legislation, and a lack of evidence-based policy is unlikely to reduce harm, and will not help those in the direst need.


A summary of the Psychoactive Substances Act 2016 is available here, as well as the full text.