But study co-author Dr. Robert West of University College London pointed out that the United States and Canada had among the highest rates of dependence on opioids (650 cases per 100,000), cocaine (301 cases per 100,000) and marijuana (749 cases per 100,000 people), according to U.S. News and World Report. Overall, the rates of marijuana and opioid dependence were about three times higher than the rest of the world.
"The U.S. has major research agendas moving forward to advance our knowledge-base in order to inform policy and practice regarding how to best address this problem," Berg said. "Surveillance is a key part of monitoring the problem, informing interventions, and evaluating policies and practices that are adopted and implemented."
Berg said that broad international studies, such as this one, help researchers better understand differences in drug use across countries.
"Not all countries regulate alcohol and tobacco in similar ways nor have policies or practices in place that aim to address specific aspects of behavior related to alcohol and tobacco use," Berg said.
"Social norms are also quite different in relation to the use of these substances, particularly among different genders within a country or within other sub-populations," she explained. "Understanding these different multilevel factors and their impact on alcohol- and tobacco-related consequences are key to informing how countries like the U.S. should address this critical issue."
Berg adds that this kind of study is "critical" in helping researchers and governments understand the societal and individual costs of substance abuse. It also gives a better picture of how legalization and regulation impact usage and dependence.
"There could be a great deal to be learned from countries or areas of the world with lower prevalence of opioid dependence and areas of the world that have combated opioid dependence successfully," she said. "This speaks to how critical international research is to informing policy and practice."