Why people can't spot cannabis intoxication (but can detect alcohol)

A new study reveals that laypeople struggle to accurately identify cannabis intoxication, though they perform better at detecting alcohol impairment. Researchers surveyed 467 Australian participants about the cues they use to spot intoxication in others. While most of the cues people reported were factually accurate—including physical signs like coordination issues and behavioral changes—substantial gaps in cannabis knowledge were identified. Participants provided significantly fewer cues for cannabis intoxication compared to alcohol, suggesting limited public understanding of how cannabis affects observable behavior.

The research highlights important implications for high-risk contexts like healthcare, law enforcement, and workplace safety. Interestingly, people who used cannabis monthly or less frequently demonstrated greater accuracy in identifying cannabis intoxication cues, suggesting that casual users may actually observe effects more carefully. Those who viewed cannabis detection as difficult tended to report less accurate cues, indicating that confidence and familiarity matter significantly for intoxication detection. The study emphasizes that while laypeople possess some accurate knowledge, widespread education about diverse intoxication cues—particularly for cannabis—is urgently needed to improve public safety in situations where recognizing impairment is critical.

The findings underscore a critical knowledge gap in the era of cannabis legalization and increased use. As cannabis becomes more socially normalized and legally available in many regions, the inability to reliably detect intoxication poses real public health challenges. Better education about observable signs of cannabis impairment could improve decision-making in healthcare settings, reduce risks on roadways, and create safer workplaces. The research suggests that addressing these knowledge gaps through targeted education could meaningfully improve safety outcomes in contexts where recognizing impairment is essential.