The effect of anodal transcranial direct current stimulation on affective impulsivity in methamphetamine users: A randomized experimental study

Abstract Background and Aims Methamphetamine use disorder (MUD) is associated with significant impairments in impulsivity control, contributing to relapse and poor treatment outcomes. Transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex (DLPFC) may be helpful in modulating these symptoms. This study aimed at [1] investigating the differential effects of anodal and cathodal tDCS on craving, affective impulsivity, and motor impulsivity; and [2] exploring the correlations between changes in affective impulsivity & drug craving, and alterations in resting‐state electroencephalography (Rs‐EEG) microstate parameters following tDCS interventions. Design A randomized, parallel, double‐blind experimental study. Setting Two drug rehabilitation centers in China, from June 2022 to June 2023. Participants One hundred male participants (ages 33.7 ± 6.26 years) during rehabilitation for MUD. Intervention Participants were randomly assigned to anodal (n = 33), cathodal (n = 31), or sham (n = 36) tDCS conditions. tDCS was delivered at 2 mA (anodal and cathodal) or 0 mA (sham) for 20 minutes, twice daily for ten consecutive days. The central electrode was placed on the left dorsolateral prefrontal cortex. Measurements Primary and secondary outcomes were assessed at four time points: baseline (before intervention), post‐intervention 1 (after two sessions), post‐intervention 2 (after 20 sessions, primary time‐point), and one‐month follow‐up (post‐intervention 3). Primary outcomes were affective impulsivity and motor impulsivity. Secondary outcomes included drug craving, Rs‐EEG microstates, and adverse effects. Findings Anodal tDCS statistically significantly improved affective impulsivity control after 20 sessions (estimate = −36.23, 95% confidence interval [CI] [−59.72, −12.73], p < 0.01) but not motor impulsivity control. Both anodal and cathodal tDCS statistically significantly reduced drug craving after 20 sessions (anodal: estimate = 3.36, 95% CI [1.15, 5.57], p < 0.01; cathodal: estimate = 2.62, 95% CI [0.34, 4.9], p = 0.02). Changes in affective impulsivity were statistically significantly correlated with alterations in Rs‐EEG microstate parameters, such as microstate B coverage (r = 0.29, p. < 0.01, n = 100); however, there is a lack of clear evidence for correlations between changes in craving and microstate parameters. Conclusions Among methamphetamine users in rehabilitation, anodal transcranial direct current stimulation (tDCS) over the left dorsolateral prefrontal cortex appears to improve affective impulsivity control, but not motor impulsivity control, and both anodal and cathodal tDCS reduce drug craving.