Cannabis package warnings about psychosis were most educational and best at discouraging youth use | Research

The takeaway

In a survey of 1,000 US adults, cannabis warnings about psychosis risk were rated most educational and most effective for discouraging youth use, while addiction warnings were least believable.

Cannabis regulators, public health communicators, and packaging designers.

Psychosis warning rated most educational and best for discouraging youth use

What the researchers found

Among 1,000 US adults (500 cannabis users, 500 tobacco-using non-cannabis users), the psychosis warning was rated most educational and most frequently selected as best for discouraging youth use. The addiction and psychosis warnings were rated less believable than the driving warning. Any warning increased perceived harmfulness of smoking cannabis compared to no warning. Warning effects were similar across dried flower and edible product types.

Why it matters

As US states legalize cannabis, packaging warning requirements need evidence-based design. This is among the first studies comparing specific warning messages for cannabis products.

The numbers in context

1,000 adults; psychosis warning: learned most (users B=0.88, non-users B=1.60); addiction warning less believable (users B=-1.04, non-users B=1.17); any warning increased perceived harmfulness (all p<0.05).

How the study worked

Randomized online survey experiment assigning 1,000 US adults to view no warning or one of four warnings (psychosis, addiction, no FDA oversight, impaired driving) on either dried flower or edible cannabis packaging images. Linear regression analyzed perceptions.

What this study cannot tell us

Online survey (hypothetical packaging, not real-world); single exposure (does not test wear-out effects); US adults only; self-reported perceptions may not predict behavior change; tobacco-using control group may not represent general non-users.

How to read the evidence

Moderate: randomized experiment with adequate sample, but hypothetical packaging and single exposure.

When this study was published

Published 2020.

The bigger picture

The finding that warnings about psychosis (used in Canada but not the US) were most impactful suggests US cannabis packaging regulations could benefit from adopting health-specific warnings rather than generic ones.

Questions still open

Do cannabis warning labels actually change purchasing or consumption behavior? Would repeated exposure cause "wear-out" reducing effectiveness?

Common questions

What cannabis warning labels work best?

This study found warnings about psychosis risk were most educational and most effective for discouraging youth cannabis use. Warnings about addiction were the least believable. Any warning increased perceived harmfulness compared to no warning.

Do warnings need to be different for different product types?

No. Warning effects were similar across dried flower and edible packaging, suggesting a single warning design could work across product types.

Read the original research

Perceptions of U.S. and Canadian Cannabis Package Warnings Among U.S. Adults.

Drug and alcohol dependence, 217, 108275

View on PubMed ↗Publisher’s paper ↗

Citation

Pepper, Jessica K; Lee, Youn Ok; Eggers, Matthew E; Allen, Jane A; Thompson, Jesse; Nonnemaker, James M. (2020). Perceptions of U.S. and Canadian Cannabis Package Warnings Among U.S. Adults.. Drug and alcohol dependence, 217, 108275. https://doi.org/10.1016/j.drugalcdep.2020.108275