Transcranial Direct Current Stimulation (tDCS) as an intervention to improve empathic abilities and reduce violent behavior in forensic offenders: study protocol for a randomized controlled trail.
Authors: Sergiou Carmen Silva , Woods Adam J , Franken Ingmar H.A. , Dongen Josanne D.M. van 
Published: July 2019

Abstract
Background
Recent studies show that changes in one of the brain areas related to empathic abilities (i.e. the Ventromedial Prefrontal Cortex (vmPFC)) plays an important role in violent behavior in abusers of alcohol and cocaine. According to the models of James Blair, empathy is a potential inhibitor of violent behavior. Individuals with less empathic abilities may be less susceptible and motivated to inhibit violent behavior, which causes a higher risk of violence. Recent neuroscientific research shows that modulating (stimulation or inhibition) certain brain areas could be a promising new intervention for substance abuse and to reduce violent behavior, such as the neurostimulation technique Transcranial Direct Current Stimulation (tDCS). This study aims to investigate tDCS as an intervention to increase empathic abilities and reduce violent behavior in forensic substance use offenders.

Methods/design
A total sample of 50 male forensic substance abuse patients (25 active + 25 sham stimulation) will be tested in a double-blind placebo-controlled study, from which half of the patients will receive an active stimulation + treatment as usual (TAU) and the other half will receive a sham stimulation (placebo) + TAU. The patients in the active condition will receive multichannel tDCS stimulation targeting bilateral vmPFC two times a day for 20 minutes for five consecutive days. Before and after the stimulation period, the patients will complete self-report measurements, perform the Point Subtraction Aggression Paradigm (PSAP) and a passive viewing empathy task. Resting state electroencephalography (rsEEG) will be measured before and after the treatment period. A follow-up will be conducted after six months. Primary outcome is to investigate multichannel tDCS as a new intervention to increase empathic abilities and wit that reduce violent behavior in offenders with substance abuse problems. In addition, it will be studied whether electrophysiological responses in the brain are affected by the tDCS intervention. Lastly the effects of tDCS on reducing craving will be investigated.

Discussion
This study protocol describes the design of an intervention using multichannel tDCS targeting the vmPFC. This study will explore the opportunities to introduce a new intervention to improve empathic abilities and reduce violence in forensic substance use offenders. In addition, this study may help to reduce craving. The study will contribute to knowledge about increasing empathic abilities and the functioning of the vmPFC. Specifically, this study may give insight in how to implement the tDCS intervention in the setting of daily clinical practice for this complex, multiple problem target group and with that contribute to reduction of recidivism.

Trial registration
Dutch Trial Register, identifier: NTR7701. Registered on 12 January 2019; prospectively registered before the recruitment phase. https://www.trialregister.nl/trial/7459