Sleep disturbance in schizophrenia spectrum disorders: more than just a symptom?

Sleep disturbance is commonly reported in patients with schizophrenia spectrum disorder (SSD) in the clinical setting. Sleep features can be assessed subjectively, with self-report sleep questionnaires, and objectively with actigraphy and electroencephalogram recordings. Traditionally, electroencephalogram studies have focused on sleep architecture. More recently, numerous studies have investigated alterations in sleep-specific rhythms, including electroencephalogram oscillations, such as sleep spindles and slow waves, in patients with SSD compared with control subjects. Here, I briefly discuss how sleep disturbance is highly prevalent in patients with SSD and I present findings from studies demonstrating abnormalities in sleep architecture and sleep-oscillatory rhythms, with an emphasis on sleep spindles and slow-wave deficits, in these patients. This increasing body of evidence highlights the importance of sleep disturbance in SSD and points to several future research directions with related clinical implications, thus showing that sleep disturbance is more than just a symptom in these patients.