Which Cannabis Risks Did Young Adults Misjudge?
Short answer: Young adults generally recognized the risks of frequent use, family history, smoking or vaping, and higher-potency THC products. They had more difficulty distinguishing some polysubstance and potency scenarios.
How did the researchers test risk perception?
McMahon and colleagues recruited 653 Canadian adults ages 18 to 25. Participants read five short scenarios about cannabis use. Each scenario varied one feature: frequency of use, simultaneous substance use, family history of mental illness or substance use disorder, method of consumption, or product potency.
After each scenario, participants rated overall danger and expected effects on cognitive, physical, and mental health. This design measured perceived risk. It did not expose participants to cannabis and did not measure actual injury, intoxication, or impairment.
Which differences did participants recognize?
Participants rated more frequent consumption as riskier than less frequent use. They also perceived greater risk when a scenario included a family history of psychosis or substance use disorder. Smoking and vaping were rated as riskier than consuming edibles, and higher-potency THC-dominant products were generally rated as riskier than lower-potency CBD-dominant products.
Those patterns show that many participants understood several central harm-reduction messages.
Where did risk distinctions become less clear?
The study found that participants rated simultaneous cannabis and tobacco use as riskier, but did not distinguish cannabis-plus-alcohol from cannabis alone in the same way. They also did not clearly distinguish between the two higher-potency THC conditions presented in the vignettes.
That does not establish that every participant misunderstood cannabis. It shows that group ratings did not consistently track all of the risk gradations built into the scenarios.
Why this matters when evaluating statements and warnings
A person may know that “high THC” carries more risk while lacking a clear understanding of how much potency changes risk. Someone may recognize the hazards of smoke exposure while underestimating the combined effects of cannabis and alcohol. General awareness and precise risk comprehension are different things.
In a legal or clinical record, a signed warning, label, or general education statement therefore does not necessarily prove that a person understood a particular interaction, potency, or mental-health risk. The content, clarity, timing, and audience matter.
What the study cannot prove
The participants responded to hypothetical scenarios. Their answers do not establish how they behaved in real situations. The study also cannot show that education alone changes cannabis use or prevents harm. It identifies where communication may need to be more specific.
A better reader question
Instead of asking whether young adults “know cannabis is risky,” ask which risk they understood: frequency, potency, route, family history, or combined substance use. That narrower question produces more useful evidence.
Scientific source
McMahon I, Harris-Lane LM, Donnan J, Bishop L, Harris N. Emerging adult perceptions of higher-risk cannabis consumption behaviours. Harm Reduction Journal. 2023;20:127. PubMed and full-text record. DOI.
