Perceptions that substances are harmful help protect against their use. The purpose of this study was to investigate adolescent perceptions of the harmfulness of everyday and occasional use of cannabis compared to those for cigarettes, nicotine vapes, and alcohol, and how those perceptions varied with age. Participants were 160,222 adolescents who took the 2019–2020 California Student Tobacco Survey and 14,922 adolescents who took the 2024 California Youth Tobacco Survey. Descriptive statistics were used to examine harm perceptions by substance use history, use frequency, the proportion of friends using a substance, and grade level. In the 2019−2020 survey, everyday use of cannabis was perceived as harmful by the smallest proportion of adolescents (66.8%), followed by alcohol (77.7%), vapes (85.3%), and cigarettes (92.6%; all p’s < 0.0001). Harm perceptions for each substance were lower for occasional use than for everyday use, and lower among those who had ever used the substance than among those who had never used it. Harm perceptions remained unchanged or increased with grade for cigarettes, vapes, and alcohol but decreased for cannabis. For each substance, harm perceptions declined as the proportion of participants’ friends who used the substance increased. Data from the 2024 survey followed similar patterns. Adolescents perceived cannabis as less harmful than cigarettes, nicotine vapes, and alcohol. As adolescents aged, they were less likely to perceive cannabis as harmful, unlike other substances. Increased education and prevention messaging may be needed to raise awareness of the risks of using cannabis during adolescence. • This study compared adolescent harm perceptions for several commonly used substances. • Adolescents perceived cannabis as less harmful than cigarettes, nicotine vapes, and alcohol. • Cannabis harm perceptions declined with age, unlike those for other substances. • Harm perceptions for cannabis were strongly influenced by friends’ usage patterns.
Agarwal et al. (Fri,) studied this question.