Real-Time Antecedents of Young Adults' Vaping and Co-Vaping of Nicotine and Cannabis: An Ecological Momentary Assessment Study.

Background: Nicotine and cannabis vaping are common among young adults and can potentially lead to adverse health consequences. Identifying real-time antecedents of vaping events may provide insights into intervention targets pertinent to these behaviors. This study aimed to examine real-time antecedents of nicotine and cannabis vaping and same-occasion co-vaping among young adults. Objective: This study aims to examine real-time antecedents of nicotine and cannabis vaping and same-occasion co-vaping among young adults. Methods: We collected ecological momentary assessments (EMAs) via a smartphone app among California young adults (ages 18-29 y) in 2023-2024. Participants completed four random prompts each day for 30 consecutive days. Outcomes were defined as whether participants reported being about to vape nicotine, cannabis, or both substances (same-occasion co-vaping) in a given EMA. We used mixed-effects logistic regression models to examine real-time antecedents of each outcome. Results: Overall, 113 participants (mean age 23.8 y, SD3 y, 63% female, n=70) completed 9001 EMAs. Similar antecedents of all 3 vaping outcomes were craving and using alcohol. Increased cravings for a given substance were associated with a higher likelihood of vaping that substance or co-vaping. Craving for cannabis vaping was associated with lower odds of reporting nicotine vaping (adjusted odds ratio [AOR] 0.87, 95% CI 0.82-0.92). Feeling happier was associated with higher odds of reporting co-vaping (AOR 1.13, 95% CI 1.01-1.27) while feeling more stressed was associated with lower odds of vaping nicotine (AOR 0.95, 95% CI 0.91-0.98) or cannabis (AOR 0.91, 95% CI 0.86-0.97). Seeing tobacco advertisements was associated with higher odds of vaping nicotine (AOR 3.09, 95% CI 1.48-6.46) and co-vaping (AOR 4.15, 95% CI 1.18-14.52). Cannabis vaping was more likely to occur in the afternoon (AOR 1.52, 95% CI 1.16-1.98) and nighttime (AOR 1.95, 95% CI 1.45-2.63) than in the morning. Co-vaping was also more likely to occur in the afternoon (AOR 1.59, 95% CI 1.14-2.22) and nighttime (AOR 1.84, 95% CI 1.26-2.71) than in the morning, but the association was not held for nicotine vaping. Nicotine vaping was more likely to occur on weekends compared to weekdays (AOR 1.25, 95% CI 1.09-1.45), but no significant associations were found for cannabis vaping and co-vaping. Conclusions: We found similar antecedents (craving and alcohol use) and unique antecedents (mood, advertising exposure, and time of day) for nicotine vaping, cannabis vaping, and same-occasion co-vaping, suggesting targets for future vaping cessation interventions.