New study proposes public health guidelines to reduce the harms from cannabis use

More than one in ten Canadian adults, and about one in three young people aged 16-25, report using cannabis during the past year. Despite the prevalence and health risks associated with cannabis use, the study points out that Canada has not yet taken a public health approach to address its harms, as we have with alcohol, tobacco, and even injection drug use.

"A broad-based public health approach to cannabis use would include a prevention strategy for young people, risk reduction strategies for at-risk users, and better access to treatment for problem users," explains Dr. Fischer. His latest study addresses the risk reduction component, based on a comprehensive review of existent scientific data identifying the preeminent cannabis use patterns and practices leading to key health risks and harms. Based on this evidence, guidelines are offered on how to modify these practices and patterns at the user-level as a public health-oriented policy tool to reduce the harms.

"Misinformation about cannabis can be dangerous," Dr. Fischer explained. For example, surveys show that many young cannabis users believe that it is safe to drive after using cannabis, whereas recent research in Canada shows that a significant number of traffic fatalities in young adults are attributable to cannabis use. "This resembles the situation forty years ago, when the majority of Canadians still believed it was safe to drink and drive," said Dr. Fischer.

"Cannabis is not a benign drug." Dr. Fischer continued. "The evidence linking patterns of use and problems is strong. We can use this evidence to provide straightforward, factual information to cannabis users and their families, friends or peers, on how to reduce the risks for problems, and to create screening tools for health professionals to help address the risks."

Some of the harmful practices and patterns of use documented in the study include:

• Cannabis use at a young age -- Longitudinal studies suggest that using cannabis from a young age can be associated with a number of problems, including mental illness and dependence. While most cannabis users will not progress to other illicit substance use, those who use cannabis from a young age are far more likely to make this transition.
• Frequent use -- Using cannabis often, usually defined as daily or near-daily use, has been linked to a variety of health problems, including cognitive and memory performance, or risk for dependence.
• Cannabis use before driving -- Recent data suggests that approximately five percent of Canadian adult drivers report driving after cannabis use in the past year, and high school student surveys show that more students drive after cannabis use than after drinking alcohol. It is recommended that anyone using cannabis should not drive for three to four hours after consumption.
• Cannabis use during pregnancy -- While the possible consequences of cannabis use during pregnancy have not been reliably distinguished from the potentially confounding impact of alcohol and tobacco use, there is sufficient scientific basis to recommend abstinence from cannabis use during pregnancy.

"A key message is that the most reliable way to avoid cannabis-related harms is to abstain from use," said Dr. Fischer. "Those who do use cannabis need to be advised about patterns of use to avoid problems in the short and long run. Our guidelines are meant to target the most dangerous patterns of use among those citizens who use cannabis, and therefore reduce the possible health problem consequences of such use."

Using scientific evidence to provide guidelines on practices or patterns of use that substantially reduce the risks of acute and long-term harms is analogous to the 'Low Risk Drinking Guidelines' for alcohol, which were first introduced in the 1990s. "Given the prevalence and age distribution of cannabis use in Canada, a public health approach to cannabis use -- including prevention strategies for young people, risk reduction, and access to treatment -- is overdue," Dr. Fischer stated.

The Canadian Public Health Association endorses the Lower Risk Cannabis Use Guidelines. "The next step is for health and education authorities and the wider community to begin discussion of the evidence-based guidelines, and how this information could best be conveyed to key target groups in the context of a broad-based public health approach," Dr. Fischer said.

*"CIHR/PHAC" refers to the Canadian Institutes of Health Research/Public Health Agency of Canada