Hughes & Winstock  helpfully overview how different European countries have used various systems other than criminal law to control the current rapid emergence of a myriad of substances which, for the want of a better term, are often called ‘legal highs’. By going beyond simple but time-consuming criminal law, and instead using controls stemming from consumer safety or medicines legislation, this also avoids criminalization of young people. Other significant advantages of not invoking criminal law are that research on these substances is less hampered, it may be easier for problematic users to come forward for help and criminal gangs are not implicitly invited to trade in the banned substance. Furthermore, bans on specific substances may also affect the development of new therapeutic drugs, especially if analogue legislation is applied as it is in the United States. As Nutt points out , the structure of mephedrone is remarkably similar to bupropion.
Nevertheless, these suggestions do not circumvent the crucial question of what constitutes a harmful substance. As the authors point out, the concept of ‘safety’ underpins legislation of controlled marketing and unrestricted sale. The ‘potential harm’ of new substances may be especially difficult to assess. If, as suggested by Hughes & Winstock, marketing regulation law may be susceptible to different interpretations and motives, responses might not always be proportionate or timely. Indeed, it may be equally if not more prone to societal and media pressures than previous decisions under criminal law. Clear, objective criteria need to drawn up for what constitutes harm (or potential harm) in order to avoid these issues. Precautionary control of any new substance suspected of being used for its psychoactive effects may be a disproportionate response. As the UK Independent Scientific Committee of Drugs (ISCD) argues, we need a minimum data set (MDS) on which to evaluate the potential harms of all drugs. An MDS would document a drug's pharmacology, basic toxicology and human psychopharmacology and, especially if conducted on an international (e.g. Europe-wide) basis, would not be costly.
Limited research has been carried out on the effectiveness of different drug control systems, so we have a poor evidence base on which to make informed decisions. The legal status of a drug may not be critical for users. For example, when previous users of ecstasy were asked why they had quit, legal concerns were at the bottom of a hierarchy of 24 possible reasons . Again, in a recent study of 501 young cannabis users we questioned, only 16 (3.2%) had changed their use of cannabis after it was moved from class C to class B (Morgan & Curran, unpublished observations). We also happened to be in the middle of a 1-year longitudinal study of ketamine users when the UK government decided to classify it as class C . Opportunistically, we asked our 90 participants how this had affected their use and beliefs about the drug. Only one of our participants said it had affected him—he had decreased use due to a decline in the quality of ketamine available. While legal status may affect some aspects of drug use (i.e. availability and purity), it may be less likely to have an effect on the behaviour of those currently using. Further, a drug's legal status may have negligible effect on young peoples' willingness to try a new legal high; lack of harms, high purity and positive ratings from others appear to be more important factors .
It is imperative to determine how banning a substance impacts upon the use of other, potentially more harmful substances. An interesting observation by Bird  was that cocaine-related deaths reduced significantly in the period before mephedrone was banned. After the ban, 55% of the mephedrone users we questioned had increased their use of other drugs . This is not surprising in the context of the meteoric rise in mephedrone use coinciding with a marked decline in the proportion of ecstasy tablets containing MDMA by early 2009 . It will be important to research the effects of temporary bans on legal highs, such as the current UK ban on methoxetamine (MXE), a drug to which some ketamine users turned when the supply of that drug ran dry. These shorter-term bans need to achieve the intended assessment of the relative harms of new drugs in terms of at least the MDS.
Drug users appear to approach substances according to behavioural economic principles, whereby the drug of choice can shift dynamically according to variations in price, purity and availability . If so, efforts to change the availability of a substance offer only a partial solution, and will reduce harm only if other available substances are less harmful. Furthermore, efforts to restrict availability may prove ever more challenging as sophisticated web-based technologies facilitate the unrestricted sale of substances online . In reality, the supply side is infinitely adaptable, with any number of chemists willing to manufacture promising molecules for profit.
We agree with Hughes & Winstock about the benefits of using a range of approaches other than simple criminal law to control the supply of legal highs and the importance of researching the effectiveness of these differing approaches. In our view, it is critical that we do not focus exclusively on supply but also research the demand side of legal high use. How and why are different drugs substituted for each other? How do consumers choose to use and change their use of legal highs in terms of the market in established illicit psychotropics? What factors affect their motivation to use any drug or drug combination? How does prohibition or any other control mechanism affect this?
Declarations of interest