A recent study has examined the effects of transcranial direct current stimulation (tDCS) on individuals experiencing both depression and anxiety. The research, published in Biological Psychiatry: Cognitive Neuroscience and Neuroimaging by Elsevier, indicates that tDCS may have a dual impact on this population.
The study involved 101 participants diagnosed with both depression and anxiety. They were divided into two groups: one received a single 30-minute session of tDCS targeting the frontal cortex, while the other group received sham or placebo stimulation. After the intervention, all participants performed an attentional control task involving fearful face distractors during MRI scanning, followed by an eyeblink startle test under threat of mild electrical shock.
Researchers found that those who received tDCS showed improved accuracy and reaction times as well as increased activation in brain regions linked to executive function. However, contrary to their expectations, tDCS did not reduce sensitivity to threats.
Dr. Ironside explained, "Compared to the sham stimulation, frontal tDCS increased the activation of the bilateral inferior frontal gyrus (a part of the brain thought to be associated with attention) when the task was more cognitively demanding and, unexpectedly, increased amygdala (a region which has been described as the brain's 'alarm system') response when the task was less cognitively demanding. We did not see expected effects (i.e., decreased amygdala) in the fearful face condition. We also observed that tDCS increased eyeblink startle response under conditions of unpredictable threat."
Major depressive disorder remains difficult to treat effectively for many patients; over half do not respond to initial treatments and relapse rates are high. Comorbid anxiety can make treatment even more challenging.
Editor-in-Chief Cameron S. Carter from University of California Irvine School of Medicine commented on these findings: "Compared to other brain stimulation technologies, tDCS is more clinically feasible and scalable with the development of home-use devices, relying on remotely supervised protocols that support recent efforts to increase telehealth options, especially in rural areas and other situations where access to in-person mental healthcare is limited. However, tDCS is not yet an established treatment for more difficult-to-treat patients such as those with mixed anxiety and depression. This study helps shed light on the potential usefulness of this tool in this population."
Dr. Ironside concluded: "The jury is still out on whether tDCS can be a helpful treatment for anxiety and depression, although the recent FDA approval of home tDCS for depression is promising. More research is needed to better understand how tDCS works and for whom it is most effective. Our study suggests that frontal tDCS may increase task engagement; this makes the case for further investigations pairing tDCS with therapies that would benefit from increased attention/engagement."
