Abstract
Psychopathology is a ubiquitous phenomenon resulting from complex interactions between nature (i.e., environment) and nurture (i.e., biology) that is proving to be an increasingly burdensome public health concern across the globe. Classic consensus-derived, pathognomonic approaches to mental illness have numerous recognised limitations leading to widespread attempts to derive new biomarker-led, transdiagnostic classification systems that better ‘carve nature at its joints’. In parallel, the many known shortcomings of traditional first-line therapies (i.e., pharmacotherapy & psychotherapy) have precipitated endeavours to discover clinically impactful treatments that better target the putative underlying causes of these disorders. By taking a transdiagnostic, brain-centric perspective and combining it with novel, computer-based assessment and treatment methods, this thesis illustrates a systematic approach to merge those efforts at challenging the orthodoxy.
Through our literature review, we identified three key knowledge gaps in the current literature: 1) what is the evidence that specificity (i.e., modulation of the targeted EEG variables) contributes to the clinical responses from EEG neurofeedback therapy in people with internalizing disorders (IDs) such as major depressive disorder (MDD) and generalized anxiety disorder (GAD)? 2) is the triple-network model (i.e., dysfunction within and between the default mode, central executive, & salience networks) valid in ID populations using source-localised EEG? and 3) can source-localised, infraslow (<0.1 Hz) neurofeedback (ISF-NFB) targeting the triple-network be efficacious in the treatment of IDs? To answer these questions, we 1) undertook a systematic review of all the randomised, double-blind, sham-controlled trials in ID populations, 2) performed a cross-sectional study utilizing high-density (64 channel), broad-band (0.01-44 Hz), source-space EEG to compare the brain activity and connectivity between ID and non-ID populations, and 3) conducted a randomised, double-blind, sham-controlled trial of ISF-NFB in adult females with IDs.
The research reported herein found 1) the evidence for EEG neurofeedback specificity is tenuous, at best, 2) the triple-network model is valid in IDs per source-space, high-density EEG neuroimaging, and 3) ISF-NFB appears to be efficacious in the treatment of females struggling with IDs, albeit in the absence of specific treatment effects. Ultimately, it is my hope that our novel findings serve to inform ongoing efforts to improve both the diagnosis and treatment of IDs.