Current Status of Electroencephalography Microstate in Psychiatric Disorders: A Systematic Review and Meta-Analysis.

Background: Electroencephalography microstates are promising biomarkers for psychiatric conditions, although prior meta-analyses mainly focused on schizophrenia (SCH) and mood disorders. This study expands the analysis to a wider range of mental disorders, examining microstate variations across the psychosis and mood spectra and assessing medication effects in SCH.

Methods: Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, we conducted a comprehensive literature search, identifying 24 studies meeting inclusion criteria. Analyses were performed across 2 psychiatric subgroups: psychotic disorders and mood disorders. We further conducted a subgroup analysis within the SCH spectrum to examine differences in microstate properties between medicated and unmedicated patients.

Results: Microstate C demonstrated a significant increase in coverage and occurrence in patients with SCH, first-episode psychosis, and high risk of psychosis and increased duration in SCH. The absence of increased occurrence in medicated patients with SCH suggests that this feature may be state dependent or modulated by treatment. In contrast, microstate D exhibited significant decreases in duration and coverage in unmedicated patients with SCH, indicating potential links with acute psychotic states.

Conclusions: Our findings suggest that microstates C and D could serve as potential biomarkers in SCH, with microstate D alterations linked to acute psychotic symptoms and microstate C potentially reflecting a chronic course or treatment effects. These results emphasize the clinical potential of microstate analysis in psychotic disorder diagnosis and treatment monitoring. The literature on microstate variations in neurodevelopmental and mood disorders is limited, highlighting the need for further research to determine their biomarker potential in these conditions.