Transcranial random noise stimulation (tRNS) over the left dorsolateral prefrontal cortex ameliorates emotion dysregulation and executive function: a single-blind, randomized, sham-controlled clinical trial

BACKGROUND: Emotion regulation involves executive functions like inhibitory control and working memory, strongly linked to the left dorsolateral prefrontal cortex (DLPFC). This study examined whether transcranial random noise stimulation (tRNS) over the DLPFC could mitigate negative affect and associated regulatory failures induced by exposure to traumatic images in healthy individuals, serving as an experimental model of acute emotional challenge that taxes emotion regulation systems. METHODS: Sixty participants were randomized to six groups (n = 10): Sham, Emotion Dysregulation (Edys), Left tRNS (L-tRNS), Bilateral tRNS (LR-tRNS), Edys + L-tRNS, and Edys + LR-tRNS. Edys was induced via 50 traumatic images. tRNS (2 mA, 20 min) was applied unilaterally (Left DLPFC) or bilaterally (with anodal electrodes over F3/F4 and cathodal placements over F1/F5/AF3/FC3 or F2/F6/AF4/FC4, respectively). Assessments pre- and post-intervention included the Difficulties in Emotion Regulation Scale (DERS), Paced Auditory Serial Addition Test (PASAT), Emotion Regulation Questionnaire (ERQ), and Cognitive Emotion Regulation Questionnaire (CERQ). RESULTS: Emotion dysregulation induction significantly increased DERS scores and impaired PASAT performance. Active left unilateral tRNS following induction produced the greatest improvements in emotion regulation and executive function measures compared to sham and induction-only groups. Bilateral tRNS effects were smaller and inconsistent. Unilateral Left DLPFC stimulation was more effective than bilateral in transiently improving these processes. CONCLUSIONS: tRNS over the Left DLPFC may facilitate regulatory and executive functions during transient emotion dysregulation in healthy individuals. These preliminary findings from a non-clinical sample suggest that neuromodulation may facilitate emotion regulation during emotional challenge. The small sample size necessitates caution and replication. TRIAL REGISTRATION: Iranian Registry of Clinical Trials, IRCT20170417033485N2, registered on 2025/07/25.