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Study breakdown

Warning Labels on Cannabis Posts Reduce Sharing and Dampen Brain Self-Relevance

Randomized Controlled TrialModerate evidence
The takeaway

Warning labels on social media cannabis posts reduced sharing intentions in 1,776 people and decreased brain activity in self-processing regions in a neuroimaging sub-study.

Social media policy designers, public health communicators, cannabis regulation researchers

Warning labels reduced both sharing intentions and brain self-relevance activation

What the researchers found

An online experiment (N=1,776) found cannabis warning labels reduced sharing intentions. A parallel neuroimaging study (N=40) showed warning labels decreased activation in brain regions associated with self-processing compared to unlabeled cannabis posts, suggesting labels work by making content feel less personally relevant.

Why it matters

Social media is a primary vector for cannabis content among young people. Understanding both the behavioral and neural mechanisms of warning labels informs evidence-based content moderation strategies.

The numbers in context

N=1,776 for behavioral experiment. N=40 for neuroimaging study. Warning labels reduced sharing intentions and decreased self-processing brain region activation compared to unlabeled cannabis posts.

How the study worked

Two parallel studies: an online experiment testing warning label effects on sharing intentions (N=1,776) and a neuroimaging study examining brain activity changes (N=40), both conducted in the U.S.

What this study cannot tell us

Lab-based sharing intentions may not reflect actual social media behavior. Small neuroimaging sample. Warning label designs may vary in effectiveness. Does not assess long-term habituation to labels.

How to read the evidence

Large behavioral experiment plus neuroimaging validation provides strong mechanistic evidence, though lab settings may not perfectly reflect real social media behavior.

When this study was published

2025 dual-method study combining behavioral and neuroimaging approaches.

The bigger picture

This dual-method approach, combining behavioral data with brain imaging, provides the strongest evidence yet for how warning labels work: not just by adding friction, but by actually changing how the brain processes the relevance of cannabis content.

Questions still open

  • Do warning labels lose effectiveness with repeated exposure? Which label designs are most effective? Could social media platforms implement these labels at scale?

Common questions

Do warning labels on cannabis posts actually work?
Yes. This study found warning labels reduced people's intentions to share cannabis content on social media. Brain imaging revealed the labels work by making the content feel less personally relevant.
How do warning labels change how people think about cannabis content?
Brain imaging showed that warning labels decreased activation in regions associated with self-processing, suggesting labels shift content from feeling personally relevant to feeling more impersonal, which reduces the urge to share.

Read the original research

Pictorial warning labels reduce sharing intentions, blunt self-relevance processes elicited by social media posts promoting cannabis edibles.

The Journal of communication, 75(5), 321-334

Citation

Minich, Matt; Cotter, Lynne M; Kriss, Lauren A; Lu, Linqi; Yang, Sijia; Cascio, Christopher N. (2025). Pictorial warning labels reduce sharing intentions, blunt self-relevance processes elicited by social media posts promoting cannabis edibles.. The Journal of communication, 75(5), 321-334. https://doi.org/10.1093/joc/jqaf012

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