According to the neurocognitive model of addiction, the development and maintenance of drug addiction is associated with cognitive control deficits, as well as decreased activity of prefrontal regions, especially the dorsolateral prefrontal cortex (DLPFC). This study investigated how improving executive functions (EFs) impacts methamphetamine-use disorder, which has been less explored compared to craving, but might be a central aspect for the therapeutic efficacy of DLPFC stimulation in drug addiction. We assessed the efficacy of 10 repeated sessions of transcranial direct current stimulation (tDCS) over the DLPFC on executive dysfunctions in methamphetamine-use disorder, and its association with craving alterations. 39 of 50 initially recruited individuals with methamphetamine-use disorder who were in the abstinent-course treatment were randomly assigned to "active" and "sham" stimulation groups in a randomized, double-blind parallel-group study. They received active (2 mA, 20 min) or sham tDCS for 10 sessions over 5 weeks. Performance on major EF tasks (e.g., working memory, inhibitory control, cognitive flexibility, and risk-taking behaviour) and craving were measured before, immediately after, and 1 month following the intervention. Participants reported abstinence from drug consumption throughout the experiment, verified by regular urine tests during the course of the study up to the follow-up measurement. The group which received active DLPFC tDCS showed significantly improved task performance across all EFs immediately after and 1 month following the intervention, when compared to both pre-stimulation baseline and individuals who received sham tDCS. Similarly, a significant reduction in craving was observed immediately after and 1 month following the intervention in the active, but not sham stimulation group. A significant correlation between cognitive control improvement and craving reduction was found as well. Improvement of cognitive control functions is closely associated with reduced craving. Repeated DLPFC stimulation in order to improve executive control could be a promising approach for therapeutic interventions in drug addiction. However, the observed findings require further confirmation by studies that measure relapse/consumption of the respective substances over longer follow-up measurements.

Obsessive-compulsive disorder (OCD) is associated with a high disease burden, and treatment options are limited. We used intensified electrical stimulation in two dosages to target a main circuitry associated with the pathophysiology of OCD, left dorsolateral prefrontal cortex (l-DLPFC), and pre-supplementary motor area (pre-SMA) and assessed clinical outcomes, neuropsychological performance, and brain physiology. In a double-blind, randomized controlled trial, thirty-nine patients with OCD were randomly assigned to three groups of sham, 2-mA, or 1-mA transcranial direct current stimulation (tDCS) targeting the l-DLPFC (F3) and pre-SMA (FC2) with anodal and cathodal stimulation respectively. The treatment included 10 sessions of 20-minute stimulation delivered twice per day with 20-min between-session intervals. Outcome measures were reduction in OCD symptoms, anxiety, and depressive states, performance on a neuropsychological test battery (response inhibition, working memory, attention), oscillatory brain activities, and functional connectivity. All outcome measures except EEG were examined at pre-intervention, post-intervention, and 1-month follow-up times. The 2-mA protocol significantly reduced OCD symptoms, anxiety, and depression states and improved quality of life after the intervention up to 1-month follow-up compared to the sham group, while the 1-mA protocol reduced OCD symptoms only in the follow-up and depressive state immediately after and 1-month following the intervention. Both protocols partially improved response inhibition, and the 2-mA protocol reduced attention bias to OCD-related stimuli and improved reaction time in working memory performance. Both protocols increased alpha oscillatory power, and the 2-mA protocol decreased delta power as well. Both protocols increased connectivity in higher frequency bands at frontal-central areas compared to the sham. Modulation of the prefrontal-supplementary motor network with intensified tDCS ameliorates OCD clinical symptoms and results in beneficial cognitive effects. The 2-mA intensified stimulation resulted in larger symptom reduction and improved more converging outcome variables related to therapeutic efficacy. These results support applying the intensified prefrontal-SMA tDCS in larger trials.

Jaber Alizadehgoradel, Saeed Imani, Vahid Nejati, Marie-Anne Vanderhasselt, Behnam Molaei, Mohammad Ali Salehinejad, Shirin Ahmadi, Mina Taherifard. Clin Psychopharmacol Neurosci 2021;19:653-68. https://doi.org/10.9758/cpn.2021.19.4.653

Background: Due to low adherence to treatment and side effects of pharmacotherapy, using new brain stimulation, such as transcranial direct current stimulation in patients with anxiety disorders are available. Objectives: The present research was performed to evaluate the efficacy of transcranial direct current stimulation and compare tDCS with pharmacotherapy on reduction of worry, depression, and anxiety in a group of Iranian patients with generalized anxiety disorder (GAD). Methods: This study was a quasi-experimental research. A total of 18 patients (46% females and 64% males) with GAD were randomly assigned either to tDCS, pharmacotherapy or sham conditions. Stimulation was delivered over the contralateral deltoid at 2 m/A during 20 minutes in 10 sessions of 4 weeks. Symptoms were assessed by a 7-item GAD scale, HARS, HDRS, and PSWQ in pre-test, post-test and follow up assessment (2 months later). Analysis of variance with repeated measure was used to analyze the data. Results: The results showed that both tDCS and pharmacotherapy were effective in reducing worry symptoms, also the pharmacotherapy group compared with the tDCS group and sham condition was more effective in treating of worry. Anxiety symptoms were reduced by both tDCS and pharmacotherapy and the difference between the 2 methods was not significant. Finally, the effectiveness of tDCS therapy on reducing depressive symptoms was more significant than pharmacotherapy. Conclusions: The tDCS is a promising treatment for generalized anxiety disorder, especially in depressive and worry symptoms. Keywords: Anxiety; Depression; Generalized Anxiety Disorder; tDCS; Worry