Frequency-specific QEEG spectral power correlates of positive and negative symptom severity in recent-onset schizophrenia.

Disruptions to cortical oscillatory activity are characteristic of schizophrenia spectrum disorders (SSD). The objective of this preliminary study was to explore the dimensional relationships between QEEG frequency bands and symptom domains in a Middle Eastern sample of patients with early-stage SSD. This cross-sectional study included 18 patients of Azeri ethnicity with recent-onset SSD (illness duration < 5 years) in Tabriz, Iran. Resting-state EEG was recorded with eyes-open using a 19-channel 10-20 system. Spectral power was estimated using the multitaper method across 10 frequency bands (delta to gamma 2). Spearman correlations (FDR-corrected) were performed between regional power values and the Positive and Negative Syndrome Scale item scores. Distinct frequency- and region-specific associations emerged. Higher delta power in frontal, central, and temporal regions correlated positively with positive symptom severity, particularly hallucinations and delusions. Elevated theta and gamma power in central-parietal regions were associated with greater negative symptoms (e.g., emotional withdrawal, lack of spontaneity) and general psychopathology (e.g., depression, poor attention). Conversely, lower theta, alpha, and beta power were linked to suspiciousness and grandiosity. These findings suggest that frequency- and region-specific QEEG patterns may represent preliminary electrophysiological correlates of symptom dimensions in SSD. Studying underrepresented populations is important for improving the cultural relevance and generalizability of future schizophrenia research.