Intended for healthcare professionals

Practice Clinical updates

Novel psychoactive substances: types, mechanisms of action, and effects

BMJ 2017; 356 doi: (Published 25 January 2017) Cite this as: BMJ 2017;356:i6848
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Click here for a visual overview of NPS types, common names, delivery methods and associated risks.

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  1. Derek K Tracy1 2,
  2. David M Wood3 4,
  3. David Baumeister5
  1. 1Oxleas NHS Foundation Trust, London
  2. 2Cognition, Schizophrenia and Imaging Laboratory, Department of Psychosis Studies, the Institute of Psychiatry, Psychology and Neuroscience, King’s College London
  3. 3Clinical Toxicology, Guy’s and St Thomas’ NHS Foundation Trust and King’s Health Partners, London, UK
  4. 4School of Life Sciences and Medicine, King’s College London, London, UK
  5. 5Department of Psychology, the Institute of Psychiatry, Psychology and Neuroscience, King’s College London
  1. Correspondence to: D K Tracy derek.tracy{at}

What you need to know

  • Novel psychoactive substances (NPS, “legal highs”) are compounds designed to mimic existing established recreational drugs. They can be grouped into four main categories: stimulants, cannabinoids, hallucinogens, and depressants

  • Legislation regarding NPS varies internationally. In the UK it is now illegal to distribute or sell NPS, but possession is not a criminal offence

  • NPS should not be regarded as safer than established recreational drugs

  • The most commonly clinically encountered NPS are stimulants (such as mephedrone) and cannabinoids (such as “spice”)

  • Psychiatric and rehabilitation units, prisons, and schools face particular challenges in detecting and preventing use

In 2016 the Psychoactive Substances Bill banned trading but not possession of all current and future novel psychoactive substances (NPS), sometimes incorrectly called “legal highs,” in an attempt to overcome rapid proliferation of these compounds. Over 560 substances are currently monitored by the European Monitoring Centre for Drugs and Drug Addiction, with 100 new agents identified in 2015 alone. Stimulants and synthetic cannabinoids account for the vast majority and are the types most commonly clinically encountered.1 Online purchases are increasing according to the 2016 Global Drug Survey,2 potentially in response to legislative changes, as is overall NPS use: lifetime consumption was reported by 8% of younger individuals in 2015, up from 5% in 2011, with figures relatively similar between sexes and different countries.3

Professionals report feeling less confident about managing NPS compared with established recreational drugs.4 There were 15 485 accesses to UK National Poisons Information Service TOXBASE relating to “legal highs,” “branded products,” synthetic cannabinoids, and mephedrone in 2014-15.5 Regarding harms from longer term dependence, the UK National Drug Treatment Monitoring System (NDTMS) report in 2015 described 3048 and 1370 adults with documented problematic use of mephedrone and “other” NPS respectively.6

Information on NPS primarily stems from case reports and …

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