Alterations in EEG functional connectivity in individuals with depression: A systematic review

Area of Science:

• Neuroscience
• Psychiatry
• Biomedical Engineering

Background:

• The brain functions as a network of interconnected regions, where disruptions in connectivity are linked to depression and cognitive impairments.
• Electroencephalography (EEG) offers a low-burden method for assessing functional connectivity (FC) differences.
• Understanding EEG FC in depression is crucial for elucidating the disorder's etiology.

Purpose of the Study:

• To systematically review and synthesize existing evidence on EEG functional connectivity (FC) in individuals with depression.
• To identify consistent findings and inconsistencies in EEG FC measures between depressed individuals and healthy controls.

Main Methods:

• A comprehensive literature search was conducted following PRISMA guidelines, focusing on studies published before November 2021.
• Included studies compared EEG FC measures in depression cohorts versus healthy control groups.
• Data extraction and quality assessment of EEG FC methods were performed by two independent reviewers.

Main Results:

• Fifty-two studies were identified, analyzing resting-state (36 studies) and task-related/other (16 studies) EEG FC.
• Resting-state studies found no consistent differences in delta and gamma EEG FC between groups.
• Inconsistencies in alpha, theta, and beta resting-state EEG FC, as well as task-related FC, precluded clear conclusions due to methodological variations.

Conclusions:

• Current evidence on EEG functional connectivity (FC) in depression is largely inconsistent across different frequency bands and conditions.
• Significant heterogeneity in study designs and methodologies limits definitive conclusions regarding EEG FC alterations in depression.
• Further high-quality, standardized research is essential to accurately characterize EEG FC differences and their role in the pathophysiology of depression.