Effectiveness of Transcranial Direct-Current Stimulation on Impulsivity and Anxiety in Patients with Paranoid Personality Disorder

Background: Individuals with paranoid personality disorder (PPD) usually suffer from impulsive behavior and anxiety and constantly imagine others trying to humiliate, harm, or threaten them. This disorder causes mistrust towards others and may interfere with a person's ability to form close relationships. Objectives: The present study aimed to investigate the effects of transcranial direct-current stimulation (tDCS) on impulsivity and anxiety in patients with PPD. Methods: This quasi-experimental research adopted a pretest-posttest control group design. The statistical population included all patients aged 30 – 50 years with PPD referred to psychological and psychiatric clinics and hospitals in Yazd, (Iran), in 2022. Convenience sampling was employed to select 30 individuals with PPD. The participants were randomly assigned to an experimental group (n = 15) and a control (n = 15) group using a table of random numbers. The participants completed impulsivity and anxiety questionnaires during the pretest and posttest stages. The experimental group received ten 20-minute sessions of tDCS. The collected data were analyzed using SPSS v25.0. Results: The participants included 30 men and women with PPD with an average age of 41.23 ± 8.40 years. In the posttest, the mean ± SD of impulsivity for tDCS and control groups were 54.67 ± 4.03 and 93.93 ± 3.67, respectively. Moreover, the mean ± SD of anxiety in tDCS and control groups in the posttest were 16.40 ± 2.79 and 42.39 ± 2.99, respectively. The results indicated that tDCS significantly improved impulsivity and reduced anxiety at the posttest stage (P < 0.001). Conclusions: Transcranial direct-current stimulation can alleviate impulsivity and anxiety in patients with PPD. Therefore, therapists can implement the tDCS method as a complementary therapy to improve impulsivity and anxiety in patients with PPD.