Social, policy, and public health perspectives on new psychoactive substances.

New psychoactive substances pose a particular challenge to those formulating drugs policy and related public health responses. This paper outlines some of the main issues arising from their use, with a particular focus on user perspectives. Such substances are often (at least initially) produced and distributed for different reasons than controlled drugs. They emerge in users' repertoires undetected by most monitoring systems and general population drug surveys. While reasons for use by innovators and early adopters are often in the spirit of self-experimentation, such substances may rapidly diffuse to the recreational arena as a result of enthusiastic user propagation where they act as substitutes or complements to controlled drugs. The majority of substances are believed to be sourced, albeit not exclusively, from manufacturers based in China. They are retailed to consumers through the Internet and physical shops (such as 'head' and 'smart' shops), as well as traditional 'street dealers' (although data on the significance of this latter route of supply are limited). The data required for risk assessment of the harms such substances may pose, as well as information required for accurate user-derived harm reduction advice, are often limited. Moreover, some involved in the commercial supply have deliberately misbranded products, including substituting the active substance, in apparent attempts to circumvent regulatory frameworks. This leaves users susceptible to both health and criminal justice harms. Despite various attempts to restrict the supply, they often continue to be available through the illicit market, although it is not yet possible to predict whether they will join other drugs such as MDMA and LSD as mainstays of the recreational pharmacopeia.