How much cannabis is used in a joint in Australia? An experimental investigation into use by potency and frequency

Cannabis use is highly prevalent in Australia, yet current survey metrics measure tetrahydrocannabinol (THC) exposure with limited accuracy. Often survey items measure cannabis quantity by assuming specific modes of use (i.e., 'how many joints do you use?'), which fail to capture variations in cannabis use and the diverse modes of use (e.g., joints, cones, spliffs). This study investigated how much cannabis is used in these modes of administration in an Australian sample.

Participants (N = 31, M^age  = 25.77; 51% university students) completed the Roll a Joint Paradigm in which they rolled joints, spliffs and packed cones as they would typically, using oregano as 'cannabis.' Participants then prepared each again but with cannabis of higher or lower potency.

The amount of cannabis used across different modes of administration was variable: joints (range 0.10-1.25 g), spliffs (range 0.12-1.21 g) and cones (range 0.03-0.41 g). Participants who used cannabis daily rolled three times the amount of cannabis into a joint.

The amount of cannabis used in common modes of administration may be highly variable. Daily use may be associated using larger quantities of cannabis. Titration attempts based on potency were not proportional or consistent across modes of administration. The results indicate people may adjust the quantity of cannabis based on perceived potency, however, not proportional to THC concentration. Inconsistency in the amount of cannabis used based on potency and within different modes of administration may represent a problem for self-report metrics which ask participants to report cannabis use in joints.