Will growth in cryptomarket drug buying increase the harms of illicit drugs?

BACKGROUND AND AIM Cryptomarkets-on-line, anonymous market-places for illicit goods and services that specialize mainly in drugs-account for a small but rapidly growing share of the illicit drug market in many countries. Policy responses so far are based generally on the assumption that their rise will only increase drug harms. In this contribution for debate, we question this assumption. METHODS We provide a narrative review of the emerging literature connected to drug cryptomarkets. We use MacCoun & Reuter's formula to understand the effect of population-level increases in use on total harm as depending on the level of harm associated with each unit of use. We then consider the potential for cryptomarkets to increase or decrease the harms and benefits related to each unit of drug use, with specific attention to the quality of drugs sold and the non-drug-related harms and benefits for customers. RESULTS It is likely that cryptomarkets will increase both the amount and the range of substances that are sold. However, we argue that the effects on harms will depend upon whether cryptomarkets also increase the quality and safety of products that are sold, provide harm-reducing information to consumers and reduce transactional conflict involved in drug purchasing. CONCLUSIONS There is an emerging and rapidly growing evidence base connected to the macro and micro harms and benefits of cryptomarkets for drug users. Future researchers should use appropriately matched comparative designs to establish more firmly the differential harms and benefits of sourcing drugs both on- and off-line. While it is unlikely that the on-line drug trade can be eradicated completely, cryptomarkets will respond to regulation and enforcement in ways that have complex, and sometimes unanticipated, effects on both harms and benefits.