Auditory gamma oscillations predict global symptomatic outcome in the early stages of psychosis: A longitudinal investigation.

OBJECTIVES

The gamma-band auditory steady-state response (ASSR) is thought to reflect the function of parvalbumin-positive γ-aminobutyric acid (GABA)-ergic interneurons and may be a candidate biomarker in early psychosis. Although previous cross-sectional studies have shown that gamma-band ASSR is reduced in early psychosis, whether reduced gamma-band ASSR could be a predictor of the long-term prognosis remains unknown.

METHODS

In this longitudinal study, we investigated the association between gamma-band ASSR reduction and future global symptomatic or functional outcome in early psychosis. We measured 40-Hz ASSR in 34 patients with recent-onset schizophrenia (ROSZ), 28 ultra-high risk (UHR) individuals, and 30 healthy controls (HCs) at baseline. After 1-2 years, we evaluated the global assessment of functioning (GAF) in the ROSZ (N = 20) and UHR (N = 20) groups.

RESULTS

The 40-Hz ASSR was significantly reduced in the ROSZ and UHR groups. The attenuated 40-Hz ASSR was correlated with the future global symptomatic outcome in the ROSZ, but not in the UHR groups.

CONCLUSIONS

A reduction in the gamma-band ASSR after the onset of psychosis may predict symptomatic outcomes in early psychosis.

SIGNIFICANCE: Gamma-band ASSR may be a potentially useful biomarker of the long-term prognosis in patients with recent-onset schizophrenia.