tDCS and Urge in BFRBs

The goal of this study is to find out if brain stimulation can help people stop skin-picking or nail-biting. The study wants to answer two main questions: 1. Does brain stimulation reduce the urge to pick skin or bite nails after those urges are triggered? 2. Does brain stimulation reduce how often people pick their skin or bite their nails? Participants will: * Talk about their skin-picking, nail-biting, and other mental health concerns * Be placed in situations that make them want to pick or bite * Rate how strong their urges are before and after brain stimulation Researchers will compare real brain stimulation to a placebo (a fake version that looks the same but has no effect) to see if the real stimulation works to reduce skin-picking and nail-biting urges and behaviors.