Longitudinal patterns of marijuana use across ages 18-50 in a US national sample: A descriptive examination of predictors and health correlates of repeated measures latent class membership.

BACKGROUND: This descriptive study identified latent classes of longitudinal marijuana use from ages 18 through 50 among a national sample; examined covariate associations with class membership regarding use/non-use, use intensity, and use duration; and described associations between identified latent classes and age 50 health outcomes.

METHODS: The study involved collection and primary analysis of data from 9831 individuals first surveyed as 12th graders in the national Monitoring the Future study and followed through modal age 50. Repeated measures latent class analysis was used to identify latent classes based on self-reported past 12-month marijuana use.

RESULTS: Seven latent classes of marijuana use from ages 18 to 50 were identified including Non-users (44%), two classes characterized by shorter-term use patterns (totaling 28%), and four classes characterized by longer-term moderate or heavy use (totaling 28%). Use reduction appeared particularly likely during early and late 20s. Gender, parental education, alcohol/cigarette use, religious commitment, and marital status differentiated use/non-use, use intensity, and use duration after high school. In non-causal models controlling for covariates, longer-term marijuana use classes (where use extended into the late 20s or beyond) were associated with significantly higher odds of negative health outcomes at age 50.

CONCLUSIONS: Approximately 28% of the national sample reported longer-term moderate/heavy marijuana use, which was associated with negative health outcomes at age 50. The early and late 20s may be especially important periods for marijuana use prevention and intervention efforts, which may be strengthened by recognition of characteristics that appear to have significant associations with persistent use.