Cannabis Demand and Use among Veterans: A Prospective Examination

Background: Cannabis demand (i.e., relative value), assessed cross-sectionally via a hypothetical marijuana purchase task (MPT), has been associated with cannabis use, problems, and dependence symptoms, among others. However, neither the prospective stability of the MPT, nor the cyclical relationship between demand and use over time has been investigated. Moreover, cannabis demand among cannabis using veterans has yet to be examined. Method: Two waves of data from a veteran sample (N=133) reporting current (past 6-month) cannabis use were analyzed to assess stability and change in cannabis demand over six months. Autoregressive cross-lagged panel models assessed the longitudinal associations between demand indices (i.e., intensity, Omax, Pmax, breakpoint) and cannabis use. Results: Models revealed unique directions of effects for each demand index. Baseline cannabis use predicted greater intensity (ß = .32, p<.001), Omax (ß = .37, p<.001), breakpoint (ß = .28, p<.001), and Pmax (ß = .21, p = .017) at 6-months. Conversely, baseline intensity (ß = .14, p=.028), breakpoint (ß = .12, p=.038), and Pmax (ß = .12, p = .043), but not Omax, predicted greater use at 6-months. Discussion: Cannabis demand indices demonstrated prospective stability over six months and varied along with natural changes in cannabis use. Importantly, intensity, Pmax, and breakpoint displayed bidirectional predictive associations with cannabis use, and across indices, the prospective pathway from use to demand was consistently stronger. Findings highlight the value of assessing cannabis demand longitudinally, particularly among clinical samples, to determine how demand fluctuates in response to experimental manipulation, intervention, and treatment.