Delay discounting in adults receiving treatment for marijuana dependence

Abstract

Delay discounting is an index of impulsive decision-making and reflects an individual's preference for smaller immediate rewards relative to larger delayed rewards. Multiple studies have indicated comparatively high rates of discounting among tobacco, alcohol, cocaine, and other types of drug users, but few studies have examined discounting among marijuana users. This report is a secondary analysis of data from a clinical trial that randomized adults with marijuana dependence to receive one of four treatments that involved contingency management (CM) and cognitive-behavioral therapy interventions. Delay discounting was assessed with the Experiential Discounting Task (Reynolds & Schiffbauer, 2004) at pretreatment in 93 participants and at 12 weeks posttreatment in 61 participants. Results indicated that higher pretreatment delay discounting (i.e., more impulsive decision-making) significantly correlated with lower readiness to change marijuana use (r = -0.22, p = .03) and greater number of days of cigarette use (r = .21, p = .04). Pretreatment discounting was not associated with any marijuana treatment outcomes. CM treatment significantly interacted with time to predict change in delay discounting from pre- to posttreatment; participants who received CM did not change their discounting over time, whereas those who did not receive CM significantly increased their discounting from pre- to posttreatment. In this sample of court-referred young adults receiving treatment for marijuana dependence, delay discounting was not strongly related to treatment outcomes, but there was some evidence that CM may protect against time-related increases in discounting.

Figure 1

Effect of Contingency Management Treatment on Posttreatment Delay Discounting. Participants in the three treatment conditions that provided contingency management are represented by the solid lines with rectangles, and participants in the one treatment condition that did not provide contingency management are represented by the dashed line with triangles. Assessment timepoints are plotted on the x-axis, and mean natural logarithm (ln) of k values are plotted on the y-axis. Higher ln k values indicate higher delay discounting (i.e., more impulsive decision-making). CM = contingency management.