To assess follow-up effects of a home-based, remotely supervised transcranial direct current stimulation (RS-tDCS) intervention on cognitive and emotional outcomes in individuals with multiple sclerosis (MS) and cannabis use disorder (CUD).

Up to 30% of individuals who use cannabis develop CUD. People with MS may be at risk given the high prevalence of cannabis use and potential for cannabis to exacerbate mood and cognitive symptoms. RS-tDCS targeting the dorsolateral prefrontal cortex (DLPFC) may enhance cognitive and emotional regulation, supporting recovery during cannabis reduction.

Forty-seven participants with MS and CUD were randomized (2:1) to receive 20 sessions of active or sham RS-tDCS (2.0 mA, 20 min) paired with mindfulness meditation audiotracks, five days per week for four weeks. Emotional outcomes were assessed using the Kessler Psychological Distress Scale (K10), Positive and Negative Affect Schedule (PANAS), and State-Trait Anxiety Inventory (STAI), aggregated into a composite emotional score (standardized z-scores, Cronbach’s α=0.84). Cognitive outcomes were assessed using the Brief International Cognitive Assessment for MS (BICAMS)—including the Symbol Digit Modalities Test (SDMT), Rey Auditory Verbal Learning Test (RAVLT), and Brief Visuospatial Memory Test–Revised (BVMT-R)—at baseline, post-intervention, and 3-month follow-up.

At 3-month follow-up, the active RS-tDCS group demonstrated sustained improvement in emotional outcomes (composite score, p=0.017), with significant reductions in distress, higher positive affect, and lower trait anxiety. Improvements in processing speed (SDMT) remained significant (p<0.05) in the active group, while sham returned to baseline.  At post-intervention, cognitive improvement was greater in the active group on the SDMT (p=0.019) and trended on the RAVLT (p=0.061). Active participants showed greater reduction in cannabis use over time (p<0.05).

RS-tDCS intervention produced sustained improvements in processing speed and verbal learning, emotional functioning, and reduced cannabis use in individuals with MS. These findings support the feasibility of home-based neuromodulation as a scalable intervention for co-occurring neurological and behavioral conditions.