Measuring change in anhedonia using the "Happy Faces" task pre- to post-repetitive transcranial magnetic stimulation (rTMS) treatment to left dorsolateral prefrontal cortex in Major Depressive Disorder (MDD): relation to empathic happiness

We investigated whether repetitive transcranial magnetic stimulation (rTMS) to the left dorsolateral prefrontal cortex (DLPFC) would reduce anhedonia in a sample of 19 depressed adults (M-age = 45.21, SD = 11.21, 63% women) randomized to either active or sham rTMS. To track anhedonia, patients completed the Snaith-Hamilton Pleasure Scale (SHAPS)(1) and a novel behavioral task called "Happy Faces," which required patients to interpret neutral versus various intensities of positively valenced human facial expressions. Patients had to indicate dichotomously whether any degree of positive emotion was expressed. We expected that more anhedonic patients would struggle most with low intensity happy faces; often incorrectly calling them neutral. Patients also completed a self-report measure of "empathic happiness"-i.e., vicarious joy. Measures were completed pre- to post-treatment. Results indicate rTMS to DLPFC related to improvement in interpretation of subtle forms of happiness in active rTMS patients relative to sham. Furthermore, empathic happiness and anhedonia score were significantly antagonistic across all patients.