New psychoactive substances have drastically modified the world drug ă scene. An increasingly popular class comprises synthetic or substituted ă cathinones (legal highs, research chemicals, bath salts). Among the most ă common psychoactive constituents of bath salts are mephedrone and ă methylone. Recent reports on the abuse of novel synthetic cathinone ă derivatives call attention to the serious physical and psychological ă risks resulting from their consumption, thereby emphasizing the growing ă use of these drugs might constitute an important public health issue. ă In this paper, we will review the available data regarding the use and ă effects of mephedrone and methylone in humans in order to highlight ă their impact on public health. To reach this objective, a literature ă search was performed on two representative databases (Pubmed, Google ă Scholar), the Erowid Center website (a US non-profit educational ă organization that provides information about psychoactive plants and ă chemicals), and various governmental websites. The terms used for the ă database search were ``mephedrone'', ``methylone'', ``new ă psychoactive substances'', ``synthetic cathinones'', ``substituted ă cathinones'', ``substance abuse'', ``substance use disorder'', ă ``adverse effects'', ``fatalities''. The literature search was ă limited to years 2005-2015 and led to the identification of 71 ă potentially relevant articles. ă To date, the actual prevalence rates of their use remains difficult to ă estimate. Important health-related issues have emerged in relation to ă the somatic, psychiatric, and addictive consequences of their use. The ă potential chronic health effects of their prolonged use remain to date ă unknown (e.g., reproductive toxicity, genotoxicity and carcinogenic ă potential). Treatment for patients with prolonged exposure to synthetic ă cathinones should ideally include a drug management plan coupled with ă psychotherapy taking place in a structured program of care. (C) 2016 ă Elsevier Inc. All rights reserved.