Objective:

To systematically analyze literature on the application of resting-state quantitative EEG (qEEG) as a potential biomarker for schizophrenia, emphasizing the significance of studies published after 2008 due to advancements in methodology.

Key Findings:

• Chronic schizophrenia patients showed increased delta and theta wave activity in anterior regions and decreased alpha peak frequency in posterior areas.
• These alterations were less pronounced or absent in first-episode psychosis, suggesting a potential progression with disease duration or treatment.
• A novel theta/alpha component (6–9 Hz) was identified, providing mechanistic insight into alpha slowing.
• Significant methodological heterogeneity among studies precluded meta-analysis, highlighting the need for standardized approaches.

Interpretation:

Characteristic qEEG alterations exist in chronic schizophrenia but are inconsistent in early psychosis. The unique theta/alpha signature is a promising specific biomarker due to its potential to differentiate between schizophrenia and healthy controls.

Limitations:

• Persistent methodological heterogeneity limits clinical translation, with variations in sample sizes, EEG recording techniques, and analysis methods.
• Lack of standardized multicenter protocols and longitudinal designs hampers the reliability of findings.

Conclusion:

Standardized multicenter protocols with longitudinal designs are essential before qEEG can be reliably implemented in routine schizophrenia diagnosis, potentially improving early detection and treatment outcomes.