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Alternating brain stimulation shows potential for major depression

In a pilot study, targeting alpha oscillations in the brain with transcranial alternating current stimulation, or tACS, showed potential as a therapeutic approach for major depressive disorder.

Among patients with MDD, those who received tACS at 10 Hz had better responses than those who received tACS at 40 Hz or sham stimulation at 2 weeks, according to the findings published in Translational Psychiatry.

Oscillatory activity is elevated in patients with MDD, which can lead to disrupted affective processing, Morgan L. Alexander, MD, from the psychiatry department and the Carolina Center for Neurostimulation at the University of North Carolina at Chapel Hill, and colleagues wrote. Because tACS applies a weak electric current with a sine-wave pattern to the scalp, it may be more appropriate to target oscillatory brain activity than other brain stimulation methods.

“TACS can modulate cortical oscillations that mediate cognitive function and can selectively modulate oscillations at the applied frequency,” the researchers wrote. “In addition, the side effects of tACS are mild and transient, and no serious adverse events have yet been reported.”

The investigators examined the feasibility and efficacy of tACS at 10 Hz to see if it improved depressive symptoms by renormalizing alpha oscillations in the left dorsolateral prefrontal cortex in 32 patients with MDD.

Participants were randomly assigned to one of three arms and received daily 40-minute sessions of either 10-Hz tACS, 40-Hz tACS or active sham stimulation for 5 days. The primary outcome was improvement as measured by the Montgomery–Åsberg Depression Rating Scale (MADRS), and the secondary outcome was change in alpha oscillations as measured by high-density electroencephalograms (EEG).

At 4 weeks, the results did not show a statistically significant reuction in depression symptoms in the 10-Hz tACS group compared with the sham or control groups.

However, exploratory analyses indicated a significant relationship between condition and response rates for the MADRS (2 = 7.334; p = 0.026) and Hamilton Depression Rating Scale (2 = 7.334; P = .026) at 2-week follow-up, demonstrating that the 10-Hz tACS group had a higher response rate (77.8%) than the 40-Hz tACS (30%) and sham stimulation (20%) groups.

"Now that we've documented how this kind of tACS can reduce depression symptoms, we can fine-tune our approach to help many people in a relatively inexpensive, noninvasive way," study author Flavio Frohlich, PhD, associate professor of psychiatry and director of the Carolina Center for Neurostimulation, said in a press release.

In addition, the investigators observed a significant decrease in alpha power over the left frontal regions as measured by EEG after finishing the intervention in the 10-Hz tACS group (n = 26; P < .05). Participants from all three groups reported minimal side effects, according to the study.

"It's important to note that this is a first-of-its kind study,” Frohlich said in the release. “When we started this research with computer simulations and preclinical studies, it was unclear if we would see an effect in people days after tACS treatment — let alone if tACS could become a treatment for psychiatric illnesses. So, the fact that we've seen such positive results from this study gives me confidence our approach could help many people with depression." – by Savannah Demko

Disclosure: Alexander reports no relevant financial disclosures. Frohlich reports numerous relevant financial disclosures. Please see the study for all authors’ relevant financial disclosures.