Neurocognitive Impulsivity in Opiate Users at Different Lengths of Abstinence

Background: Opiate users (OU) are characterized by impaired neurocognitive functioning reflecting risky and maladaptive decision-making  and deficient inhibitory control. Research suggests that these impairments persist even after prolonged abstinence from opiate use and may increase the risk of relapse. However, few studies have examined the effect of length of abstinence on neurocognitive functioning in OU. The aim of the current study was to examine whether length of abstinence affects different types of decision-making and response inhibition in former OU.  
Method: Participants included 45 “pure” (i.e. mono-dependent on opioids) OU in early abstinence [0-12 months], 68 “pure” OU in protracted abstinence [>12 months], and 68 matched control participants. Decision-making was assessed with the Iowa Gambling Task (IGT), a measure of decision-making under ambiguity, the Cambridge Gambling Task (CGT), a measure of decision-making under risk, and the Monetary Choice Questionnaire (MCQ), a measure of delay discounting. Response inhibition was examined with the Stop Signal Task (SST), a measure of action cancellation, and the Go/No-Go Task (GNG), a measure of action inhibition.
Results: Results revealed group differences in decision making under risk (CGT) and ambiguity (IGT), where control participants displayed better decision making compared to OU in early abstinence. Both groups of former OU were also characterized by higher discounting of delayed rewards (MCQ). Regression analyses revealed minimal effects of length of abstinence on performance on decision-making tasks and no effects on delay discounting. In addition, both OU groups showed reduced action inhibition (GNG) relative to controls and there were no group differences in action cancellation (SST). Length of abstinence had no effect on response inhibition. 
Conclusion: Our data suggests that impairments in decision-making under risk and ambiguity in OU remain notable in the earlier stages of abstinence from opiate use, but may improve with longer periods of abstinence. In contrast, deficient action inhibition and increased delay discounting may persist even after prolonged abstinence from opiate use. Overall, our findings suggest that neurocognitive function may not fully recover even with protracted abstinence, which requires the development of personalized relapse prevention and cognitive remediation programs targeting the key neurocognitive functions impaired by chronic opiate use.
Acknowledgements: This research was supported by grant R01DA021421 from the National Institute on Drug Abuse (NIDA) and the Fogarty International Center (FIC) to Jasmin Vassileva.