Latent Trajectories of Persistence of Cannabis Use Across Four Decades in 329 Men From the San Diego Prospective Study.

Objective: These analyses use data from a 40-year prospective study to extend information into the sixth and seventh decades of life regarding latent trajectory classes of cannabis use and predictors of those classes.

Method: Data from the San Diego Prospective Study were analyzed for 329 men of European and Hispanic ethnicity who had used cannabis at about age 23 at study entry (Time 1) and who were interviewed about every 5 years through about age 60 to 70. Latent classes of cannabis use trajectories were evaluated using latent class growth analyses, baseline predictors of class membership were determined, and significant predictors of each class were established using logistic regression analyses.

Results: Four latent classes were identified ranging from 12.5% with cannabis use at every follow-up to 25.8% with no use after Time 1. Eight of 14 Time 1 predictors differed significantly across the trajectory classes, including five (age, marital status, religious identity, intensity of cannabis use, and sensation seeking) that significantly contributed to regression analyses when all significant predictors were considered together.

Discussion: Forty-two percent of participants continued using cannabis long-term, including one in eight who used it at every follow-up. Predictors of continued use and identification of those most likely to stop required gathering information on a range of demographic, prior substance use, and personality characteristics.

Conclusions: Considering the potential enhanced dangers of cannabis use in later life, the high rate of continued use over four decades implies that clinicians should ask all older patients about recent cannabis use, especially if they had used it in their 20s.