Could decision-making processes, then, play a role in treatment outcome for patients with substance use disorders?
Both methamphetamine- and cocaine-dependent patients have been found to perform significantly worse on measures assessing the probability of reward vs. loss, relative to the reward�s value, such as the Iowa Gambling Task (IGT), in which subjects choose between decks of cards offering high payments with occasional high penalties or decks offering low payments but more frequent lower penalties (with the optimal long-term strategy being the second deck).
These same patients have also exhibited impaired performance on a commonly used measure of response reversal (the ability to reverse strategy in the presence of changing circumstances), the Wisconsin Card Sorting Task (WCST). In this test, subjects match 128 cards one at a time to 4 stimulus cards by clicking a mouse. After 10 correct responses in a row, the sorting principle is changed, forcing the test taker to alter their approach.
This multi-site study, part of a NIDA Clinical Trials Network protocol examining stimulant abuser groups in 12-step (STAGE-12), assessed whether performance on the IGT and WCST predicted relapse in 160 methamphetamine- or cocaine-dependent persons.
Both measures were administered shortly after treatment admission, followed by assessment of stimulant use over the next 6 months.
Results found that performance on the IGT and WCST did not significantly predict relapse status or time to relapse. Unexpectedly, in fact, worse performance on the IGT was associated with fewer number of stimulant use days, not greater.
In contrast, and more in line with the study�s hypothesis, worse performance on the WCST (suggesting an inability to adapt to a changing environment) was associated with a greater number of stimulant use days. The predictive effect of errors on the WCST on subsequent use were confined to methamphetamine-dependent and minority participants.
Conclusions: Decision-making processes, as measured in this study, do not uniformly predict relapse or subsequent use of stimulants. The contradictory IGT results could be explained by a variety of factors, including the simple fact that people who have recently been administered stimulants often have temporarily improved cognitive function compared to those who have not. However, these results certainly warrant further examination and study. More comprehensive and global measures of impulsiveness may better assess relapse risk and use.
Find it in the CTN Dissemination Library: http://ctndisseminationlibrary.org/display/1182.htm