**14. Conflicts of interest**

No conflicts of interest are declared here which may have influenced the interpretation of present data. Please note the following: JC has been the UK Focal Point expert on Drug-Related Deaths for the European Monitoring Centre for Drugs and Drugs Addiction since 2000; FS is a full member of the UK Advisory Council on the Misuse of Drugs (ACMD); JC and FS are members of the ACMD Working Group on Novel Psychoactive Substances, the UK Early Warning System. All authors are members of the International Centre for Drug Policy (ICDP). AHG is current President of the International Narcotics Control Board (INCB). The views expressed here reflect only those of authors and not necessarily those of the Department of Health, Home Office, the ACMD, the ICDP, the EMCDDA, or the INCB.
