New challenges raised by ‘legal highs’

Dr Tom Freeman and Dr Thomas Richardson respond to Lorna MacKay's letter in the February issue.

Lorna MacKay’s letter (February 2015) about novel psychoactive substances (NPSs or ‘legal highs’) raises important questions about their potential impact on mental health. We agree that there is an urgent need for research and evidence-based guidance on these new drugs, to assist service providers and users alike.

It is difficult to conduct research in the area for several reasons. Firstly, there are many different NPSs and those who use them appear to try many different types (Van Hout & Brennan, 2011). Secondly, new drugs arise quickly as existing ones are made illegal. It is therefore very difficult to examine the individual contribution of specific drugs. For example, if baseline paranoia and drug use is measured once at baseline and then repeated six months later, users may have used several different substances and started to use new ones since baseline. It is therefore difficult to determine whether any one specific substance is influencing any changes observed.

A third problem with NPSs is that despite often being ‘legal’, it is not ethical to administer them to human volunteers in a research study, because they are new substances with unknown toxicology – paradoxically, it is far safer to administer illegal drugs such as MDMA/Ecstasy or cannabis. One partial solution is to investigate NPSs naturalistically as people use self-administer these drugs themselves (as has been done by Freeman et al., 2012, with mephedrone).

Another strategy is the collection of survey data, such as the annual Global Drugs Survey founded by Dr Adam Winstock (, which was recently completed by 100,000 people in 50 countries. These data indicate that synthetic cannabinoid products (e.g. ‘Spice’) are associated with a 30-fold greater risk of emergency medical treatment than natural cannabis and elicit greater paranoia; only 7 per cent preferred them over natural cannabis (Winstock & Barratt, 2013).

Sharing information about NPSs is widespread on the internet (e.g., and other researchers have taken a resourceful approach by searching through this information, summarising it and disseminating it in a timely, accurate and accessible format. From 2010 to 2012 the Recreational Drugs European Network (ReDNet) aimed to provide such information for young people across Europe ( ReDNet identified over 650 substances (Corazza et al., 2013), and more research of this kind could be incredible valuable.

NPSs raise significant challenges for health services. Some progress has certainly been made; for example, Central London and North West London NHS Foundation Trust has a dedicated ‘club drugs’ (including NPSs) clinic run by Dr Owen Bowden-Jones (

A second clinic has recently opened in Camden and Islington, and we hope this movement will continue across the UK.

We believe that innovative research methodologies and adaptive clinical practice are needed in light of the challenges raised by NPSs. We hope that service providers will discuss NPSs with drug users and encourage them to share their experiences to take part in research in order to improve our understanding of these new drugs.

Dr Tom Freeman
University College London
Dr Thomas Richardson
Solent NHS Trust Portsmouth and University of Southampton

Corazza, O. et al. (2013). Promoting innovation and excellence to face the rapid diffusion of novel psychoactive substances in the EU: The outcomes of the ReDNet project. Human Psychopharmacology: Clinical and Experimental, 28(4), 317–323.
Freeman, T.P., Morgan, C.J., Vaughn-Jones, J. et al. (2012). Cognitive and subjective effects of mephedrone and factors influencing use of a ‘new legal high’. Addiction, 107(4), 792–800.
Van Hout, M.C. & Brennan, R. (2011) ‘Heads Held High’: An exploratory study of legal highs in pre-legislation Ireland. Journal of Ethnicity in Substance Abuse, 10(3), 256–272.
Winstock, A.R. & Barratt, M.J. (2013). Synthetic cannabis: A comparison of patterns of use and effect profile with natural cannabis in a large global sample. Drug and Alcohol Dependence, 131(1), 106–111.

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