Quantification and comparison of marijuana smoking practices: Blunts, joints, and pipes (2011)

The quantification method for collecting self-reported marijuana use data is not standardized as it is for alcohol or cigarettes, which presents a methodologic challenge for marijuana use disorder treatment studies. Serum and urine markers of marijuana use have a long half-life, limiting their utility as a clinical trial outcome measure. Structured calendar-based interview procedures can accurately measure the frequency of self-reported marijuana use, but are unable to reliably address issues such as quantity of use or potency. This study compared the quantity and assigned-dollar value among users of blunts, joints, and pipes enrolled in two clinical trials testing pharmacotherapies for marijuana dependence. The timeline follow-back method was modified to incorporate using a surrogate substance to represent marijuana to enable participants to estimate the amount and value used. Blunt users were mostly black and Hispanic, while users of joints and pipes were primarily white. Participants reported that they placed 50% more marijuana in blunts than in joints and placed more than twice the amount of marijuana in blunts than in pipes. These findings demonstrate the feasibility of using a surrogate weight estimation procedure to augment calendar-based methods of measuring self-reported marijuana use. Individual variability in use practices limits the utility of this method to estimating within-subject comparisons, rather than between subject comparisons. [Author's abstract]