PATH to understanding cannabis and nicotine initiation and co-use among emerging adults.

Objectives: The purpose of this study was to describe the characteristics and age of initiation of nicotine and cannabis use, with a particular focus on the emerging adult period (ages 18-24 years) and concurrent use of nicotine with cannabis.

Design: A secondary analysis of Population Assessment of Tobacco and Health (PATH).

Sample: 32,078 participants from a nationally representative study of tobacco use and health outcomes.

Measurement: Variables of interest included ever use, regular use and age of initiation (first-time use) of nicotine (including tobacco) and/or cannabis and selected demographic factors.

Results: Ever-use of nicotine was associated with a 13-fold increase in the likelihood of having ever used cannabis. Among those who reported cannabis use, 96.4% had also used nicotine. While initiation in adolescence was most common, 27.1% of those who use nicotine and 34.9% of those who use cannabis initiated during emerging adulthood. Among regular users of nicotine, 41.5% began regular use in emerging adulthood.

Conclusions: These findings underscore the continued susceptibility of emerging adults to initiation of these substances. Co-use of nicotine and cannabis is an understudied phenomenon in emerging adults with significant potential to cause harm and should be a public health priority.