A study of adults abstinent from methamphetamine found greater slowing when participants anticipated having to stop, while estimated stopping speed did not differ significantly from controls. Preparation and last-moment cancellation therefore gave different accounts of inhibitory control.
Dai and colleagues compared 35 adults with methamphetamine use disorder and 35 controls using a conditional stop-signal task. The methamphetamine group, recruited from compulsory rehabilitation centers in China, had been abstinent for an average of about 265 days. This was an observational comparison of human groups; investigators did not administer methamphetamine.
Some blocks required responding without preparing to stop. Others required readiness to cancel a response if a stop signal appeared. The additional response time in the uncertain condition was the preparation cost. Stop-signal reaction time estimated the speed of reactive cancellation.
Mean preparation cost was approximately 130 milliseconds in the methamphetamine group and 93 milliseconds in controls, a significant difference (p = 0.004). Estimated stop-signal reaction time was approximately 265 versus 260 milliseconds and did not differ significantly (p = 0.667). Accuracy also showed no significant overall group effect.
The authors interpreted the larger preparation cost as less efficient proactive control: participants slowed more while achieving similar task performance. It would be misleading to turn that finding into either uniformly impaired inhibition or complete recovery of every inhibitory process.
Participants were not followed from active use through abstinence. Consequently, the study cannot establish that abstinence caused reactive stopping to recover, or that the preparation difference was caused by methamphetamine rather than pre-existing characteristics or treatment context. The modest sample also limits subgroup conclusions.
These computer-task outcomes are not drug concentrations, and the study established no individual impairment or driving threshold. Its practical contribution is to show why an assessment should identify the particular inhibitory process measured rather than treating all stopping tasks as interchangeable.
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Patients with Methamphetamine Use Disorder Show Highly Utilized Proactive Inhibitory Control and Intact Reactive Inhibitory Control with Long-Term Abstinence. doi:10.3390/brainsci12080974.