The hidden-zero effect in male individuals with opioid use disorder.

Background

Explicitly expressing the hidden opportunity cost in intertemporal choice significantly reduces healthy participants' delay discounting - a phenomenon named the "hidden-zero effect," which is undetermined in individuals with substance use disorder (SUD).

Objectives

This study aimed to determine whether the hidden-zero effect occurs among individuals with opioid use disorder (OUD) and the degree to which this effect differs between the OUD group and healthy controls.

Methods

In two different experiments, Exp#1) 29 male individuals with OUD (13.5 ± 6.0 months abstinence) and 29 male controls performed an intertemporal choice task (ICT); Exp#2) 28 male individuals with OUD (17.5 ± 5.6 months abstinence) and 27 male controls performed a delay discounting task (DDT). The OUD group was recruited from a mandatory treatment, and controls from WeChat. There were two choice conditions in both two tasks: the hidden-zero (H0) condition (standard), and the explicit-zero (E0) condition (explicitly expressing opportunity cost).

Results

Compared with the H0 condition, all participants' delay discounting was significantly decreased in the E0 condition (ps < .05, ηp2 = 0.254, 0.110). There was no significant difference in the changed degree between these two groups in either experiment (ps > .05). The delay discounting of the OUD group was significantly higher than that of controls only in Experiment 2 (p < .001, ηp2 = 0.376).

Conclusion

This study extended the population in which the hidden-zero effect occurs to individuals with OUD. With respect to delay discounting, the hidden-zero effect benefit did not differ in OUD and control participants.