Transcranial Direct Current Stimulation for Depression

Background:

Depression is a common mental disorder characterized by persistent low mood and anhedonia. Pharmacological and psychotherapeutic treatments demonstrate only moderate efficacy. Non-invasive brain stimulation techniques offer novel therapeutic approaches. Among these, transcranial direct current stimulation (tDCS) holds advantages due to its simplicity, low cost, and minimal side effects, exhibiting good efficacy and tolerability in depression treatment. The dorsolateral prefrontal cortex (DLPFC), a core region of the cognitive control network, serves as a traditional target for non-invasive brain stimulation in depression and plays a crucial role in positive affect (PA) processing. Conversely, the dorsomedial prefrontal cortex (DMPFC), a central region of the default mode network, participates in negative self-referential processing and negative affect (NA) regulation, demonstrating potential as a novel therapeutic target.

Objective:

Given the distinct roles of DLPFC and DMPFC in different affective regulation networks, this study aims to investigate the differential effects of tDCS targeting these regions on emotional regulation in patients with depression.

Design:

This study employed a randomized, double-blind, controlled design. Inpatients with depression were recruited from the Department of Psychology and Sleep Medicine at the Second Affiliated Hospital of Anhui Medical University. Participants were randomly assigned to receive either effective tDCS targeting the left DLPFC or effective tDCS targeting the DMPFC. Both groups will receive tDCS treatment twice daily for 5 consecutive days. Each session lasts 20 minutes at 2mA, with a minimum 4-hour interval between sessions. Before the start of tDCS treatment and after completion of all sessions, clinical psychologists conducted standardized assessments and collected EEG data from the patients. Assessments included tests of associative memory, the Self-Rating Depression Scale (SDS), the 17-item Hamilton Depression Rating Scale (HAMD), Hamilton Anxiety Rating Scale (HAMA), 15-item Somatic Symptom Severity Scale of the Patient Health Questionnaire (PHQ-15), PHQ-15), the Insomnia Severity Index (ISI), the Positive and Negative Affect Scale (PANAS), and the Ruminative Responses Scale (RRS). Follow-up was conducted after one month, during which only the HAMD scale was assessed. Primary clinical outcomes included changes in HAMD scores at baseline, post-treatment, and 1-month follow-up; number of responders and remitters post-treatment (response defined as >50% reduction in HAMD score at endpoint; remission defined as HAMD score ≤7 at endpoint); improvement in PANAS scores post-treatment; correlation between HAMD improvement and PANAS improvement. Secondary outcomes included changes in residual scale scores post-treatment, changes in EEG signals in stimulated brain regions, and changes in functional connectivity across the entire brain.

Inclusion criteria

• The diagnosis meets the criteria for depression outlined in the Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5).
• Age between 18 and 65 years.
• Education level exceeding 5 years, with no significant hearing or visual impairments.
• Voluntary signing of informed consent and ability to cooperate with general demographic data collection and neuropsychological scale testing.

Exclusion criteria

• Age under 18 or over 65.
• Patients with neurological disorders such as epilepsy or severe physical illnesses.
• Patients with comorbid neuropsychiatric disorders, such as schizophrenia or obsessive-compulsive disorder.
• Patients unable to undergo tDCS treatment for any reason, including presence of ferromagnetic metal in the head or implanted medical devices in the head/neck region.
• Pregnant or lactating women.