The findings of a proof-of-concept study in JAMA Psychiatry demonstrated that amygdala threat reactivity was reduced in women immediately after a session of transcranial direct-current stimulation.
The authors of this community-based, randomized clinical trial identified 18 women aged 18 to 42 (mean age, 23) years who scored higher than 45 on the trait subscale of the State-Trait Anxiety Inventory. Left-handed individuals were excluded. Participants received either real or sham stimulation of the dorsolateral prefrontal cortex followed by real or sham stimulation 1 month later, and each visit included functional magnetic resonance imaging and a visual identification task.
Final analyses included 16 women, 8 in each group. Transcranial direct-current stimulation appeared to decrease bilateral amygdala threat reactivity (z=3.30, P =.04), increase cortical activation, and improve task accuracy by 12.2%, or 2.2 answers per person (P =.04). In addition, investigators observed that stimulation of the dorsolateral prefrontal cortex reduced amygdala threat reactivity and increased activity in key nodes of the dorsal and ventral attentional control centers simultaneously.
A strength of the study was the use of functional magnetic resonance imaging. A lack of neuroimaging-based evidence makes it difficult to draw a causal link between brain stimulation and its effects.
As the study involved only a single session of transcranial direct-current stimulation, the enduring efficacy of the treatment was not clear. Additionally, the findings may not generalize to male patients.
Ironside M, Browning M, Ansari T, et al. Effect of prefrontal cortex stimulation on regulation of amygdala response to threat in individuals with trait anxiety: a randomized clinical trial [published online October 17, 2018]. JAMA Psychiatry. doi:10.1001/jamapsychiatry.2018.2172