Motivations for Marijuana Use Among Young Adults in the U.S

Introduction: Marijuana is the most frequently used drug after alcohol, although it remains illegal in the majority of the U.S. and is associated with negative consequences including decreased cognitive ability, unsafe driving, and addiction. Marijuana users may engage in use for a variety of reasons, and understanding these motivations for use may be key to identifying individuals at risk for escalating use.

Methods: Data from the Monitoring the Future (MTF) panel study from 1976-2013 is used.  The MTF follow-up surveys are designed to follow selected high school seniors who participated in the main MTF study as they progress through adulthood. Latent Class Analysis (LCA) was used to identify a set of latent classes of individuals based on responses to a set of thirteen categorical, observed variables regarding motives for marijuana use. The analysis sample consisted of respondents that used marijuana in least one of the three follow-up interviews conducted at modal ages 19/20 (FU1), 21/22 (FU2), or 23/24 (FU3), N=6,071 (53.5% women, 79.4% White, 7.8% Black, and 13.1% Hispanic/Other).

Results: LCA was performed separately for each follow-up group using PROC LCA and %LCABootStrap.  Both techniques were implemented via user-defined SAS macros and executed within SAS software. Initial model fitting was done using PROC LCA and %LCABootstrap including 2-8 LCA classes within each follow-up group, with non-users excluded.  Results suggested 5 distinct latent classes for each follow-up interview, based on fit statistics and model interpretability. Non-users were included in a subsequent LCA analysis that suggested 6 latent classes. The classes of marijuana use motives were: (1) Non-users (24% at FU1, 28% at FU2, 37% at FU3), (2) Experimenters (10%, 7%, 5%), (3) Use for a good time or to get high (30%, 31%, 29%), (4) Use for a good time and relaxed highs (15%, 16%, 12%), (5) Use for a relaxed high (14%, 12%, 12%), and (6) Use as a way to deal with emotional problems (7%, 6%, 5%).

Conclusion: These classes of marijuana use motives suggest distinct profiles underlying marijuana use that persist across young adulthood. The extent to which individuals transition into and out of these classes over time will also be examined using Latent Transition Analysis. Implications for intervention include the need for specific motivational tailoring in efforts to reduce marijuana use and related problems.