Community-Based Tdcs Treatment for Depression: Acceptability and Neuropsychological Correlates

This thesis brings together 3 novel projects about major depressive disorder (MDD) and transcranial direct current stimulation (tDCS). The first project addresses acceptability and efficacy of tDCS in late-life depression (LLD) using a meta-analysis of individual-level patient data from randomised sham-controlled trials. Bayesian techniques answer two questions; Is active tDCS over dorsolateral prefrontal cortex (DLPFC) efficacious and considered acceptable in LLD compared to sham. It is hypothesised active tDCS over DLPFC will improve symptoms associated with LLD compared to sham and will be considered acceptable in LLD. Results show there is an 82% probability of a small effect and no statistical difference between dropout rates for acceptability. Project 2 addresses a qualitative analysis of acceptability using a new paradigm to investigate the feasibility and acceptability of at-home tDCS. The aim is to investigate the acceptability of at-home tDCS in MDD using qualitative methods by answering How do patients with depression describe the acceptability of using a novel treatment, at-home tDCS? Data collected via semi-structured interviewing conducted at 2 timepoints: post 21st session (final) and at 6 months follow up. Thematic analysis identified 4 main themes were classified: Side effects, Effectiveness, Time commitment, Support. Project 3 uses Auditory Verbal Learning Task to assess verbal learning with the research question was “Does verbal learning improve over time following tDCS treatment for MDD?”. Treatment was hypothesised to be associated with improved verbal learning skills, as measured by total learning, and learning over trials, in line with McClintock et al (2020) findings. Assessments occurred at 3 timepoints after a tDCS sessions on: 1st session, the 10th session (after 2 weeks) and the 21st session (final). Contrary to the hypothesis, no statistically significant results were elicited. This was not expected but are in line with some reports. The final chapter takes the opportunity to discuss further the results of each project in more detail and the impact that COVID-19 may have on MDD research in the future.