Products and patterns through which adolescents, young adults, and adults initiate co-use of tobacco and cannabis

Background: Co-use of tobacco and cannabis is common. However, few studies have examined the temporal sequencing through which individuals initiate co-use, and how these patterns vary across age. This study addresses this gap by examining the specific products and temporal sequencing through which adolescents, young adults, and adults initiate co-use of tobacco and cannabis. Among adolescents, young adults, and adults who co- used tobacco and cannabis in the past 30 days, we examined (a) whether tobacco or cannabis was used first in their lifetime and (b) which specific tobacco or cannabis product (e.g., nicotine e-cigarettes, cannabis edibles) was the first used. Methods: Data were from a cross-sectional national survey (N = 6,131, 13-40 years old) in which participants reported ever use, past-30-day-use, and order of use for 17 different tobacco and cannabis products. Results were analyzed overall and by age group (13-20; 21-24; 25-40). Results: 38.4% of participants reported use of both tobacco and cannabis in the past 30 days. Among these participants, 70.9% used tobacco first in their lifetime (66.6% < 21; 71.7% 21-24; 76.6%> 24). Approximately 60% of participants who initiated co-use with tobacco reported nicotine e-cigarettes as their first tobacco product (63.3% < 21; 66.7% 21-24; 49.6%> 24). Conclusions: The majority of participants who used both tobacco and cannabis used tobacco first in their lifetime, and nicotine e-cigarettes were the most common form of tobacco initiation, particularly among adolescents and young adults. Findings emphasize the need for co-use prevention programs to target common products of initiation.