Gamma transcranial alternating current stimulation improves mood and cognition in patients with major depression.

Major depression is one of the most common psychiatric disorders with a high rate of treatment resistance where new treatment options are urgently warranted. One of these new options are non-invasive brain stimulation techniques like transcranial magnetic or electric stimulation. One of the latter is transcranial Alternating Current Stimulation (tACS) in various frequencies. Here, we report a case series of six patients suffering from major depression treated with tACS in gamma (40 Hz) frequency. Patients were randomized to two groups, receiving either two 10-min stimulations (group 1) or a 20-min stimulation or per day (group 2) over ten days. Hamilton Depression Rating Scale and Beck Depression Inventory decreased during treatment in both study groups by 85% and 78% (group 1), or 62% and 24% respectively (group 2). Results also showed an improvement in cognitive functions assessed by word fluency and n-back test. It is hypothesized that gamma tACS could help to synchronize disturbed frequency bands in frontal and prefrontal cortex areas and thus restore dysbalanced neural connectivity in psychiatric disorders.