Canadian Centre on Substance Use and Addiction

Early and Regular Cannabis Use Is a Strong Predictor of Cognitive Impairment

Ottawa, April 5, 2019 — Starting to smoke cannabis earlier in life — before 16 or 17 — is one of the strongest predictors of noticeable cognitive difficulties according to a new report released by the Canadian Centre on Substance Use and Addiction (CCSA).

Clearing the Smoke on Cannabis: Regular Use and Cognitive Functioning looks at current research on how cannabis affects the mental processes that allow individuals to carry out regular everyday tasks such as speaking and remembering.

Although early and regular cannabis use is associated with cognitive difficulties, the report also finds the impact of regular cannabis use on these functions is generally mild for most people. Many of the measurable effects on cognitive functions disappear after sustained periods of not using cannabis.

The report includes the following additional findings:

  • Regular cannabis use is associated with changes in brain structure and function, including changes to the brain’s natural reward pathways.
  • Individuals who display risky and impulsive decision making are more likely to develop problematic cannabis use and cannabis use disorder.
  • Establishing a standardized measurement of cannabis use, including frequency of use, dosage and methods of consumption, is required to explore the causal nature of these relationships.

“The current evidence suggests that regular cannabis use is not associated with severe cognitive impairment. Instead, the effects are relatively mild and are no longer noticeable after about a month of abstinence. This means that regular cannabis use might not affect a person’s ability to perform simple, routine and everyday tasks,” explains Dr. Robert Gabrys, research and policy analyst at CCSA. “However, among individuals in safety-sensitive jobs, such as police officers and air traffic controllers, a slight deficit in concentration, judgment or problem solving may be extremely important. With the recent legalization of non-medical cannabis, an objective presentation of the evidence found in reports like this can be very valuable in informing policy and the development of public education resources.”

This report is the latest addition to CCSA’s Clearing the Smoke series on cannabis. The series looks at how cannabis use affects the mental and physical health of Canadians. Additional reports in the series address cannabis and maternal pregnancy, cannabis and driving, and cannabis use during adolescence.

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