Recent Evidence of Non-Rapid Eye Movement Sleep Oscillation Abnormalities in Psychiatric Disorders.

Purpose of review: We review recent studies published from 2019 to 2024 examining slow waves and sleep spindles abnormalities across neurodevelopmental, mood, trauma-related, and psychotic disorders using polysomnography and Electroencephalogram (EEG).

Recent findings: Individuals with attention-deficit/hyperactivity disorder (ADHD) showed higher slow-spindle activity, while findings on slow-wave activity were mixed. Individuals with autism spectrum disorder (ASD) showed inconsistent results with some evidence of lower spindle chirp and slow-wave amplitude. Individuals with depression displayed lower slow-wave and spindle parameters mostly in medicated patients. Individuals with post-traumatic stress disorder (PTSD) showed higher spindle frequency and activity, which were associated with their clinical symptoms. Psychotic disorders demonstrated the most consistent alterations, with lower spindle density, amplitude, and duration across illness stages that correlated with patients' symptom severity and cognitive deficits, whereas lower slow-wave measures were present in the early phases of the disorders. Sleep spindle and slow-wave abnormalities are present across psychiatric populations, with the most consistent alterations observed in psychotic disorders. Larger studies with standardized methodologies and longitudinal assessments are needed to establish the potential of these oscillations as neurophysiological biomarkers and/or treatment targets.