Longitudinal trajectories of marijuana use in tobacco products among young adult Texas college students from 2015 to 2019.

Aims: To measure longitudinal trajectories of marijuana use in four tobacco/nicotine products (hand-rolled cigarettes/spliffs, cigars/blunts, hookah, and e-cigarettes) among young adult Texas college students from 2015 to 2019.

Design: This study used six consecutive waves of data from the marketing and promotions across colleges in Texas project (Project M-PACT), a longitudinal study of the tobacco behaviors of young adult college students. The first four waves were collected every 6 months (fall 2015-spring 2017), and the final two waves were conducted yearly (spring 2018 and 2019). Growth curve models measured trajectories of marijuana use in tobacco products across the 3.5-year period.

Setting And Participants: A total of 4857 young adults from 24 colleges in the largest metropolitan areas of Texas, United States (Austin, Dallas, Houston, and San Antonio): mean age = 21.0, SD = 2.3; 64.2% assigned female; 36.1% non-Hispanic white, 31.0% Hispanic, and 33.0% other or combination race/ethnicity.

Measurements: Participants completed online surveys assessing their past 6-month use of marijuana in four tobacco products of interest (spliffs, blunts, hookah, and e-cigarettes) and socio-demographic variables (sex, race/ethnicity, age, 2-year/4-year college attendance, and sexual and gender minority identity).

Findings: Observed vaping marijuana in e-cigarettes approximately doubled between the spring of 2015 and the spring of 2019, from 11.8% to 23.9% following a quadratic time trend (linear OR = 0.84, 95% CI = 0.73-0.97, quadratic OR = 1.18, CI = 1.13-1.22). This same time period saw a quadratic decline in using marijuana in hookah (P < 0.001) and no changes in using hand-rolled cigarettes/spliffs or cigars/blunts for marijuana delivery.

Conclusions: The popularity of nicotine e-cigarettes appears to be expanding the avenues for marijuana delivery among young adults in Texas, United States.