Efficacy and safety of transcranial Direct Current Stimulation (tDCS) in Alzheimer’s disease: systematic review and meta-analysis

We sought to assess the efficacy and safety of transcranial direct current stimulation (tDCS) in people with Alzheimer’s disease (AD), given its potential as a non-pharmacological therapeutic alternative for cognitive and neuropsychiatric symptoms. We searched PubMed, the Cochrane Library, Embase, and Lilacs from inception to November 2025 for randomised controlled trials (RCTs) of tDCS in patients with AD. Outcomes, including cognitive function, neuropsychiatric symptoms, serious adverse events, activities of daily living, and any adverse events, were analysed using Review Manager 5.4. We included 22 RCTs and 868 participants. The meta-analysis showed uncertain effects of tDCS on cognitive function assessed by the Mini-Mental State Examination at < 6 months (MD = 2.29, 95% CI = 1.04 to 3.55; very low certainty). Similarly, effects on neuropsychiatric symptoms assessed by the Neuropsychiatric Inventory remained uncertain (MD = -2.87, 95% CI = -9.20 to 3.47; very low certainty), as did the risk of any adverse events at < 6 months (RR = 1.98, 95% CI = 0.81 to 4.83; very low certainty). Results across other cognitive and functional assessment tools were also inconsistent, with substantial imprecision and heterogeneity among studies. The efficacy and safety of tDCS for the treatment of AD are uncertain. Knowledge from new trials might change the understanding of the effects of tDCS in people with AD.