Marijuana use and intoxication among daily users: An intensive longitudinal study

Abstract Background Most of the harm from marijuana use is experienced by daily users. Despite this, there has not been a detailed prospective description of daily marijuana use. Methods We recruited daily marijuana users (n = 142) by internet ads, Craigslist, flyers, etc. Participants were mostly women (58%) with a mean age of 33 and 47% were minorities. Participants called an Interactive Voice Response phone system to report marijuana and other drug use daily for 3 months. Results Participants averaged using marijuana 3.2 times per day. Almost all participants used multiple modes of delivery during the study. Bongs/vaporizers/pipes were the most common mode of use (45% of uses). Day-to-day variability in amount of use was relatively small. The median rating of intoxication was 3.8 on a 0–6 scale with no intoxication reported on 1% of days and severe intoxication on 24% of days. The large majority binge drank (71%) or used tobacco (73%). Fifteen during-study variables were associated with the frequency of marijuana use; running out of marijuana and social setting were the strongest correlates. Retrospective reports of “usual” use at study entry were often significantly different than daily reports of use during the study. Conclusions This is the first detailed prospective description of daily marijuana use. Most users used multiple times/day, used multiple modes to administer marijuana, were often intoxicated, and under-reported high rates of using alcohol and tobacco. The frequency of marijuana use was especially influenced by social factors. These results will help future studies better describe daily marijuana use.