Acute effect of twice-daily 15 mA transcranial alternating current stimulation on treatment-resistant depression: a case series study

Totheeditor:Major depressive disorder(MDD)is a principal cause of disability worldwide and is often associated with high morbidity and mortality rates.Although there are several therapies available for the treatment of depression,about one-third of patients with MMD will not respond to two or more antidepressant drugs with different mechanisms;the patients are then referred to as having treatment-resistant depression(TRD).Patients with TRD have a poorer quality of life,greater economic burden and increased suicidal behaviours.Therefore,new antidepressant treatments that are effective,safe,long-lasting and tolerable are needed.Ketamine infusion,intranasal esketamine and transcranial magnetic stimulation(TMS)have been used to treat early stage TRD.’A recent review suggests that electroconvulsive therapy(ECT)may be superior to ketamine for reducing depression severity in the acute treatment of TRD.

Brain-wide activation involved in 15 mA transcranial alternating current stimulation in patients with first-episode major depressive disorder

Background Although 15 mA transcranial alternating current stimulation(tACS)has a therapeutic effect on depression,the activations of brain structures in humans accounting for this tACS configuration remain largely unknown.Aims To investigate which intracranial brain structures are engaged in the tACS at 77.5 Hz and 15 mA,delivered via the forehead and the mastoid electrodes in the human brain.Methods Actual human head models were built using the magnetic resonance imagings of eight outpatient volunteers with drug-naïve,first-episode major depressive disorder and then used to perform the electric field distributions with SimNIBS software.Results The electric field distributions of the sagittal,coronal and axial planes showed that the bilateral frontal lobes,bilateral temporal lobes,hippocampus,cingulate,hypothalamus,thalamus,amygdala,cerebellum and brainstem were visibly stimulated by the 15 mA tACS procedure.Conclusions Brain-wide activation,including the cortex,subcortical structures,cerebellum and brainstem,is involved in the 15 mA tACS intervention for first-episode major depressive disorder.Our results indicate that the simultaneous involvement of multiple brain regions is a possible mechanism for its effectiveness in reducing depressive symptoms.