The emergence of the phenomenon of new psychoactive substances (NPS) since the mid-2000s marks a new phase in our millennia-long relationship with mood or mind-altering substances. Until the 19th century, most psychoactive substances were consumed by eating or drinking crude plant material. Developments in organic chemistry in the 19th century allowed scientists and clinicians to develop more potent forms of the active ingredients extracted from plants and to deliver medicines more efficiently through technologies like the hypodermic needle. Eventually, thousands of new medicines with psychoactive properties were synthesised, only a fraction of which were used by clinicians. Inevitably, many of the new substances developed for research or experimental purposes came to be used in non-medical ways due to lax regulation and curiosity driven by sociocultural changes.

Synthesis was not confined to research settings and drugs with no medical application, such as LSD, ketamine, PCP, and MDMA, emerged through the work of hobbyists or criminal organisations. From the 1960s, these substances found their way onto the illegal drug market alongside medicines diverted from clinical use. However, in the mid-2000s, the quantity, type, and availability of these novel substances increased dramatically as the internet provided both the scientific information required to modify existing compounds and a means to facilitate distribution. Most novel substances serve as a short-term replacement for the more established drugs and are quickly replaced by newly synthesised products as their predecessors are controlled or fall out of favour. There is frequently a danger from very high potency and from the susceptibility of inexperienced users.

Legal classification of NPS is the first step in the policy response to the problem. From early on in their emergence on drug markets, international organisations have agreed to describe them as substances not controlled under the United Nations Drug Control Conventions, the basis on which most countries establish their drug control legislation. The volume of new drugs and the frequency of novel syntheses have made legislative responses difficult, with considerable variety in the approaches taken by national governments. The scientific response, in contrast, has been highly coordinated, at least in the European Union (EU). Monitoring bodies, laboratories, and health experts have created an integrated system of early warning systems across the EU, coordinating the work of national networks and building an efficient process of identification of substances likely to cause harm, adverse event reporting, and advice for both health services and regulatory authorities.

The rapid development of Covid-19 vaccines in 2020 was one of the most remarkable achievements in scientific history. The capacity and willingness of scientists to work together across national boundaries, a capacity often not displayed by governments, was essential to the rapid development and deployment of vaccines. The threat of new drugs to public health is, of course, far smaller than that of a pandemic. We still need to prepare for a rapidly changing situation in which a highly efficient and productive drug manufacture and distribution system can quickly supply new markets that may emerge over the coming years. While there is much work to be done in early warning, the knowledge infrastructure needed to respond to this danger to public health is in place. Europe’s early warning system is an outstanding example of scientific rigour, international cooperation, and refined communication, and provides valuable lessons to other spheres of public health.