Resting-state qEEG identifies distinct neurophysiological signatures in chronic schizophrenia compared to first-episode psychosisBrain wave patterns help distinguish schizophrenia from early psychosis

Background and HypothesisSchizophrenia affects approximately 1% of the global population, with early diagnosis critical for optimal treatment outcomes. Resting-state quantitative electroencephalography (qEEG) represents a promising, non-invasive biomarker. We hypothesized that 18 years after the seminal Boutros review, advances in qEEG methodology would demonstrate characteristic neurophysiological signatures distinguishing schizophrenia from healthy controls and first-episode psychosis.Study DesignThis systematic review followed PRISMA guidelines, searching PubMed, Google Scholar, and Scopus for studies published after 2008. Inclusion criteria required adult human studies comparing resting-state qEEG in patients with schizophrenia or first-episode psychosis versus healthy controls. Studies employing advanced artificial intelligence techniques, evoked potentials, and task-based recordings were excluded to focus on classical qEEG parameters applicable in clinical settings from 467 publications after temporal restriction, 19 original studies met inclusion criteria. Across the studies included in this review, a total of 1242 patients were analyzed, comprising 981 individuals diagnosed with schizophrenia and 261 individuals with a first episode of psychosis. These cohorts were compared with 1211 healthy control participants across studies.Study ResultsChronic schizophrenia patients consistently demonstrated 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 progression with disease duration or long-term treatment. The novel theta/alpha component (6–9 Hz) identified by Nakhnikian et al. provides mechanistic insight into alpha slowing. Significant methodological heterogeneity precluded meta-analysis.ConclusionsCharacteristic qEEG alterations exist in chronic schizophrenia but remain inconsistent in early psychosis. The unique theta/alpha signature represents a promising specific biomarker. However, persistent methodological heterogeneity limits clinical translation. Standardized multicenter protocols with longitudinal designs are essential before qEEG implementation in routine schizophrenia diagnosis.