Importance: Electronic cigarette (e-cigarette) use has been reported to increase the likelihood of future cigarette smoking among adolescents. The prospective association between e-cigarette use and cannabis use has been less clear, especially in recent years.

Question: Is electronic cigarette use among cannabis-naive adolescents in the US associated with increased likelihood of future cannabis use?

Findings: With the use of longitudinal data on a nationally representative cohort of 9828 youths from 2017 to 2019, this cohort study found that cannabis-naive adolescents who have used electronic cigarettes are significantly more likely to report cannabis use 1 year later compared with those who have not used electronic cigarettes.

Meaning: The findings of this cohort study suggest that adolescent electronic cigarette use was associated with an increased likelihood of future cannabis use, but the overall association of electronic cigarette use with youth cannabis use at the population level is likely quite small.