Drug and Alcohol Dependence 72 (2003) 99–115 Review Injury risk associated with cannabis and cocaine use  Scott Macdonald a,* , Kristin Anglin-Bodrug a , Robert E. Mann b , Patricia Erickson b , Andrew Hathaway b , Mary Chipman c , Margaret Rylett a a Center for Addiction and Mental Health, 200-100 Collip Circle, Suite 200, London, Ont., Canada N6G 4X8 b Center for Addiction and Mental Health, 33 Russell Street, Toronto, Ont., Canada M5S 2S1 c Department of Public Health Sciences, University of Toronto, Toronto, Ont., Canada M5S 1A8 Received 23 January 2003; received in revised form 19 June 2003; accepted 25 June 2003 Abstract The purpose of this paper is to review the results and limitations of studies of injury risks associated with cannabis and cocaine use. Three types of fatal and non-fatal injuries are considered: injuries due to collisions, intentional injuries and injuries in general. Four types of studies were reviewed: (I) laboratory studies, (II) descriptive and analytic epidemiological studies on the prevalence of cannabis or cocaine use through drug testing of those injured, (III) studies of non-clinical samples, and (IV) studies of clinical samples of drug users. The research that utilized drug tests showed similar proportions testing positive for cannabis in fatal and non-fatal injury groups, and for collisions, violence and injuries in general. By contrast, large differences in the average proportions testing positive for cocaine were found among these same injury groups. For example, 28.7% of people with intentional injuries (primarily homicides) tested positive for cocaine, while 4.5% of injured drivers tested positive. Studies of non-clinical samples have shown that both cannabis and cocaine use are related to intentional injuries and injuries in general. Results indicate higher risk for all types of injuries among cannabis and cocaine clients in treatment. Strengths and limitations of the different types of studies are discussed. More rigorous studies are needed which should focus on ruling out alternative explanations for relationships between drug use and injuries. © 2003 Elsevier Ireland Ltd. All rights reserved. Keywords: Cannabis; Cocaine; Injuries; Accidents; Violence; Motor vehicle 1. Introduction Cannabis and cocaine are two of the most commonly used illicit drugs (e.g. Adlaf et al., 1994) and the hazards posed by these drugs to users have been the subject of considerable debate over the years (e.g. Alexander, 1990; Commission of Inquiry into the Non-Medical Use of Drugs, 1973; Erickson, 1980). A major concern about the use of any psychoactive drug is its possible influence on risk of injury from various causes, including motor vehicle collisions and violence.  The views expressed in this paper are those of the authors and do not necessarily reflect the views of the Center for Addiction and Mental Health. * Corresponding author. Tel.: +1-519-858-5000x22006; fax: +1-519-858-5199. E-mail address: scotm@uwo.ca (S. Macdonald). The purpose of this paper is to review the available em- pirical research in order to assess the risks that cannabis and cocaine may pose for traffic collisions, intentional injuries and injuries in general. The review also aims to determine whether risks of cannabis or cocaine use are the same across these injury groups and between fatal and non-fatal injuries within each injury group. The review also permits an anal- ysis of the relative dangers of each drug. The strengths and limitations of these studies and priorities for future research are identified. For this review, computerized literature searches were conducted using keywords such as cannabis, cocaine, vi- olence and injuries, with search programs (e.g. PubMed and PsychoINFO) to identify published articles. In addi- tion, manual searches of selected journals were conducted where articles on this topic are likely to be published. Bib- liographic references of recent relevant papers were also reviewed to ensure that the widest range of suitable studies 0376-8716/$ – see front matter © 2003 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/S0376-8716(03)00202-3