Management of substance abuse

The health and social effects of nonmedical cannabis use

New WHO publication on cannabis


Chapter 1. Introduction

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 (uncertainty estimates 128.5–232.1 million) (UNODC, 2015). There is a worrying increasing demand for treatment for cannabis use disorders and associated health conditions in high- and middle-income countries, and there has been increased attention to the public health impacts of cannabis use and related disorders in international policy dialogues. All this added up to the decision to publish this update report on the health and social effects of nonmedical use of cannabis.

In 1995 the World Health Organization (WHO) convened a meeting of experts on cannabis that led to the development of a report on the health consequences of cannabis use (WHO, 1997). Since then there has been significant research on the effects of cannabis use on health.

WHO (through its Department of Mental Health and Substance Abuse) organized an expert meeting on 21-23 April 2015 to review and summarize the available knowledge on the effects of nonmedical cannabis use on health and psychosocial functioning. The meeting was hosted by the Swedish Ministry of Health and Social Affairs. The purpose of the meeting was to review the latest evidence of the impact of nonmedical cannabis use on health, which is defined by WHO as a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity.[1] The meeting also addressed health system responses to cannabis-use disorders and other health conditions caused by or associated with nonmedical cannabis use. It identified priorities for international research in these areas. The medical use of cannabis and cannabinoids was outside the scope of the meeting.

The meeting was attended by experts from academia, research institutions, international organizations, national health agencies. Prior to the meeting, experts were invited to produce a series of detailed background papers on the topics to be considered. These papers informed the discussions at the meeting and the meeting report that was subsequently circulated to all participating experts. A small drafting group (consisting of Professor Wayne Hall, Professor Louisa Degenhardt, Professor Jürgen Rehm, Dr Amy Porath-Waller, Ms Maria Renström and Ms Lauren Chidsey) was formed to develop a draft document that formed the basis for this publication. The draft was circulated to meeting participants and external experts for review.

This publication builds on contributions from a broad range of experts and researchers from different parts of the world. It aims to present the current knowledge on the impact of nonmedical cannabis use on health. In the process of finalizing the current report, consideration was given to the update on cannabis and cannabis resin (Madras, 2015) commissioned by the Secretariat of the WHO Expert Committee on Drug Dependence and presented to the thirty-seventh meeting of that Expert Committee in November 2015 (WHO, 2015).



[1] Preamble to the Constitution of the World Health Organization which was adopted by the International Health Conference held in New York from 19 June to 22 July 1946, signed on 22 July 1946 by the representatives of 61 States (Off. Rec. Wld Hlth Org. 2:100), and entered into force on 7 April 1948. Amendments adopted by the Twenty-sixth, Twenty-ninth, Thirty-ninth and Fifty-first World Health Assemblies (resolutions WHA26.37, WHA29.38, WHA39.6 and WHA51.23) came into force on 3 February 1977, 20 January 1984, 11 July 1994 and 15 September 2005 respectively and are incorporated in the present text.