Effects of transcranial direct current stimulation (tDCS) in obsessive-compulsive disorder

INTERVENTION: tDCS (active condition) vs. sham tDCS (control condition) will be applied in a double‐blinded randomized cross‐over design. tDCS in the active condition will comprise 20 minutes of anodal tDCS over the preSMA region with a current of 2mA in the MRI. tDCS in the control condition will comprise 20 minutes of sham tDCS (20 sec. fade‐in, fade out) over the preSMA region. Participants are randomly assigned to the different arms using a random number generator system. CONDITION: Effects of transcranial direct current stimulation (tDCS) in patients suffering from obsessive‐compulsive disorder ; Mental and Behavioural Disorders PRIMARY OUTCOME: ; 1. Brain activation and connectivity measured during real tDCS and sham tDCS using functional magnetic resonance imaging (fMRI) during two response inhibition tasks. Real tDCS and sham tDCS take place 1 week apart.; 2. Inhibition performance measured with two well‐established inhibition tasks (Stroop task, Stop‐Signal‐task) at T0 (i.e., first MRI measurement timepoint) and T1 (i.e., 1 week later).; SECONDARY OUTCOME: Clinical symptoms assessed with the Yale‐Brown Obsessive‐Compulsive Scale (Y‐BOCS) at T0 (i.e., first MRI measurement timepoint) and T1 (i.e., 1 week later) INCLUSION CRITERIA: 1. MRI compatibility, age 18‐65 years, right‐handedness 2. OCD according to DSM‐V 3. At least a score of 8 in the Y‐BOCS scale 4. No additional psychopharmacological medication (e.g. antipsychotic medication) 5. No bipolar disorder, no schizophrenia, no schizo‐affective disorder, no posttraumatic stres disorder, no substance abuse (apart from nicotine), no personality disorder