Recent Developments in Noninvasive Neuromodulation for Mood and Anxiety Disorders

Abstract

Noninvasive neuromodulation refers to a family of device-based interventions that apply electrical or magnetic fields, either at convulsive or subconvulsive levels, to the brain through the intact skull to modulate neural function. This is a rapidly evolving field, with new research emerging regarding the various roles that these devices can play both in studying the neural mechanisms underlying mood and anxiety disorders, and in treating pharmacoresistant conditions either on their own or in combination with other therapies. Each neuromodulation modality has its pros and cons and should be carefully chosen after weighing the risks and benefits. This manuscript reviews some of the most exciting developments in this field over the past year and emphasizes themes that are emerging as being important for these tools to fulfill their potential to transform how we study and treat mood and anxiety disorders. Key among these themes is the concept of how we understand the "dose" of the stimulation, and how exogenously applied fields interact with endogenous brain activity. Refining the concept of dose will ultimately be important in allowing clinicians and researchers to apply the procedure with precision to engage the targeted network to achieve the desired effects in each individual. The large parameter space defining dose of neuromodulation makes interpreting the literature on safety and efficacy challenging and highlights the need for clear and accurate reporting of the spatial, temporal, and contextual features of dosage to make the emerging literature base as informative as possible. Ultimately, the impact of noninvasive neuromodulation devices is potentially transformational given their utility in providing mechanistic insight into the circuitbased and oscillatory origins of mood and anxiety disorders, as well as providing therapeutic interventions rationally designed to target disease-related processes.