Most people are poorly informed about cannabis health risks, especially psychosis | Research

The takeaway

Across over 72,000 respondents in the U.S. and Canada, only 23-37% knew about cannabis's link to psychosis, while 12-18% believed the false claim that cannabis can cure cancer.

Public health communicators, policymakers, and cannabis educators.

Only 23-37% knew about cannabis-psychosis link; 12-18% believed cannabis cures cancer

What the researchers found

Knowledge of cannabis health risks was highest for driving impairment (66-80%), pregnancy risks (61-71%), and addiction potential (51-62%), but lowest for psychosis and schizophrenia risk (23-37%). 12-18% agreed cannabis could cure or prevent cancer (false), and 6-7% believed it could cause diabetes (false). Canadians had the highest health knowledge, followed by U.S. legal states, then U.S. illegal states.

Why it matters

Substantial knowledge gaps, particularly about psychosis risk, could lead to uninformed decisions about cannabis use. Frequent consumers had the lowest knowledge despite the greatest exposure.

The numbers in context

72,459 respondents. Driving risk awareness: 66-80%. Pregnancy risk: 61-71%. Addiction: 51-62%. Psychosis: 23-37%. False cancer cure belief: 12-18%. False diabetes belief: 6-7%.

How the study worked

Cross-sectional online surveys from the 2018-2019 International Cannabis Policy Study with 72,459 respondents aged 16-65 recruited from Nielsen panels across Canada and U.S. states. Nine health effect questions including two false control items.

What this study cannot tell us

Non-probability sampling. Online survey may underrepresent certain populations. Self-reported knowledge may not reflect actual understanding.

How to read the evidence

Very large international sample, though non-probability online panel methodology limits representativeness.

When this study was published

Published in 2022 with 2018-2019 survey data.

The bigger picture

The finding that Canadian respondents (where cannabis is federally legal with regulated information) had higher health knowledge than U.S. respondents suggests legalization with public education may improve awareness.

Questions still open

Could better psychosis risk communication change cannabis use patterns? Why do frequent users have less health knowledge despite more exposure to cannabis information?

Common questions

What did people know least about?

The risk of psychosis and schizophrenia from cannabis use was the least known health risk, with only 23-37% of respondents aware of this association.

Did legalization improve health knowledge?

Yes. Canadian respondents (federal legalization with regulated products and information) had the highest health knowledge, followed by U.S. legal states, then illegal states.

Read the original research

Perceptions of the health risks of cannabis: estimates from national surveys in Canada and the United States, 2018-2019.

Health education research, 37(2), 61-78

View on PubMed ↗Publisher’s paper ↗

Citation

Goodman, Samantha; Hammond, David. (2022). Perceptions of the health risks of cannabis: estimates from national surveys in Canada and the United States, 2018-2019.. Health education research, 37(2), 61-78. https://doi.org/10.1093/her/cyac006