Non-invasive brain stimulation in generalized anxiety disorder: A systematic review

In the last years, several studies using non-invasive brain stimulation (NIBS) techniques demonstrated that the dorsolateral prefrontal cortex (DLPFC) plays a key role in the neurobiological bases of anxiety disorders. Both transcranial magnetic stimulation (TMS) and transcranial direct current stimulation (tDCS) applied primarily over the prefrontal cortex have been shown to modulate anxiety symptomatology and attention allocation in the generalized anxiety disorder. A literature search on PubMed and PsycINFO databases following PRISMA guidelines identified 4 TMS studies (one open-label study and three randomized trials with active/sham conditions) and one tDCS case report study that have applied NIBS in patients with GAD. All the studies targeted the DLPFC except one in which the parietal cortex has been stimulated. Overall, the findings would suggest that NIBS could ameliorate anxiety symptoms and that improvements remained stable in the follow-up. Although a limited number of NIBS studies has been conducted on patients with anxiety disorders, these techniques could represent promising tools for the study of neurofunctional basis of anxiety disorders. Further sham-controlled studies are needed to clarify the mechanisms of action of NIBS in order to optimize stimulation protocols and to verify their effectiveness for treating anxiety symptoms.