Spend today, clean tomorrow: Predicting methamphetamine abstinence in a randomized controlled trial.

Abstract

Objective This secondary analysis of data from a randomized controlled trial tested two behavioral economics mechanisms (substitutability and delay discounting) to explain outcomes using contingency management (CM) for methamphetamine dependence. Frequency and purchase type (hedonic/utilitarian and consumable/durable) of CM payments were also examined. Methods 82 methamphetamine-dependent gay/bisexual men randomly assigned to conditions delivering CM received monetary vouchers in exchange for stimulant-negative urine samples in a 16-week trial requiring thrice weekly visits (Shoptaw et al., 2005). At any visit participants could redeem vouchers for goods. A time-lagged counting process Cox Proportional Hazards model for recurrent event survival analysis examined aspects of the frequency and type of these CM purchases. Results After controlling for severity of baseline methamphetamine use and accumulated CM wealth, as measured by cumulative successful earning days, participants who redeemed CM earnings at any visit (“spenders”) were significantly more likely to produce stimulant-negative urine samples in the subsequent visit, compared to those who did not redeem (“savers”) 1.011* [1.005, 1.017], Z=3.43, p<0.001. Conclusions Findings support the economic concept of substitutability of CM purchases and explain trial outcomes as a function of frequency of CM purchases rather than frequency or accumulated total CM earnings. Promotion of frequent purchases in incentive-based programs should facilitate substitution for the perceived value of methamphetamine and improve abstinence outcomes.

Behavioral interventions for Cambodian female entertainment and sex workers who use amphetamine-type stimulants

“…Cash incentives were provided to participants at each urine screening visit as an immediate, tangible reinforcement for ATS abstinence. This is consistent with prior research where more frequent receipt of cash incentives earned in CCT was associated with greater odds of abstinence at subsequent urine screening visits (Ling Murtaugh, Krishnamurti, Davis, Reback, & Shoptaw, 2013). Where participants provided a positive urine test for ATS, they did not receive the incentive for that visit or a cash bonus for that week.…”

Commentary on Gowin et al. (2014): Brain is behavior—methamphetamine dependence and recovery

“…Another option may involve manipulating the way in which rewards are delivered. In controlled secondary data analyses, frequently spending rewards earned in a contingency management schedule (compared to saving for a high‐value good) significantly increased the likelihood that methamphetamine‐dependent individuals would appear at their next clinic visit abstinent from drug .…”

Contingency management voucher redemption as an indicator of delayed gratification

“…Second, Ling-Murtaugh and colleagues revealed a significant positive association between rates of CM voucher redemption and biomarker-confirmed substance abstinence (Ling-Murtaugh, Krishnamurti, Davis, Reback, Shoptaw 2013), corroborating the existence of an empirical link between substance use and real-life decision making. Results showed that treatment-seeking, substance-dependent gay and bisexual men were more likely to submit clean urine samples if they redeemed their CM vouchers with greater frequency, a result the authors ascribed to the “substitutability” of the rewards offered through voucher redemption.…”

“…It is unknown whether results presented here are generalizable to other (e.g., less impacted, treatment seeking) populations. For example, recall that among treatment-seeking, substance-dependent gay and bisexual men, those participants who redeemed their CM vouchers more frequently were more likely to submit clean urine samples (Ling-Murtaugh et al, 2013). Such a result contrasts with the findings presented here and may be due to the aforementioned study participants’ status as treatment-seekers.…”

“…Both of these innovative recent studies (Bickel et al 2010; Ling-Murtaugh et al 2013) reveal the importance of CM voucher redemption logs as valuable sources of data, and in combination have inspired the research question and analytical design of the current study. This prospective analysis of a randomized controlled trial tested whether the frequency of participants’ voucher redemptions during a CM intervention was associated with ongoing substance use.…”