Cannabis is globally the most commonly used psychoactive substance under international control. In 2013, an estimated 181.8 million people aged 15-64 years used cannabis for nonmedical purposes globally (UNODC, 2015). There is an increasing demand for treatment for cannabis-use disorders and associated health conditions in high- and middle-income countries. This report focuses on nonmedical use of cannabis, building on contributions from a broad range of experts and researchers from different parts of the world. It aims to present current knowledge on the impact of nonmedical cannabis use on health, from its impact on brain development to its role in respiratory diseases. The potential medical utility of cannabis - including the pharmacology, toxicology and possible therapeutic applications of the cannabis plant - is outside the scope of this report.