Frontal Stimulation to Modulate Threat Sensitivity in Anxious Depression

Study Summary

Over 50% of patients with major depressive disorder (MDD) do not respond to initial treatment and relapse is common. In particular, comorbid depression and anxiety disorders are associated with more treatment resistance. Thus, there is a great need for novel, more targeted treatments. Transcranial direct current stimulation (tDCS) is a novel intervention that can be used to causally target neural excitability and plasticity in brain regions/circuits implicated in regulating mood and anxiety and emerging evidence suggests that it reduces threat sensitivity. Here the investigators propose to use tDCS to target threat sensitivity as a core symptom of anxious depression to determine if the investigators can engage the neural circuits that are treatment targets. Following the administration of a single dose of anxiolytic or antidepressant treatment, early changes in emotional processing have been observed in healthy people and clinical groups. Among patients, acute cognitive effects - such as a reduction in threat sensitivity - have been shown to predict response to drug and behavioral treatments. Functional magnetic resonance imaging (fMRI) studies have confirmed hyperactive amygdala and/or hypoactive prefrontal activity in patients, indicating an imbalance of activity within this cortico-limbic circuit that sub-serves threat identification (amygdala) and top-down control (prefrontal). Specifically, treatments aiming to remediate prefrontal/ amygdala dysfunction could be a critical target in patients exhibiting these deficits. Several clinical trials have shown that administration of frontal cortex tDCS is a potentially effective treatment for MDD. However, underlying mechanisms of action are unclear. To meet this gap, the investigators propose an experimental medicine study (target identification and initial target engagement paths) where 141 volunteers with anxious MDD will be randomized to receive a single session of active or sham tDCS in a parallel design. Threat s

Primary Outcome

Preliminary findings show that frontal tDCS can reduce amygdala threat reactivity in high trait anxious females. The investigators seek to replicate this effect in a larger, clinical sample which also includes males. Specifically, the investigators expect that, compared to sham tDCS, the active tDCS group will show changed amygdala BOLD fMRI activation to fearful faces (difference between fearful and neutral faces), following acute tDCS administration.

Interventions

• DEVICE transcranial direct current stimulation