Abstract
Sleep disturbances are a pervasive and clinically significant feature across a wide range of psychiatric disorders. This chapter explores the complex and often bidirectional relationship between sleep and mental illness, emphasizing the diagnostic, therapeutic, and prognostic implications. Mental health disorders frequently present with insomnia, hypersomnia, or circadian disruptions. Sleep abnormalities are not merely symptoms but may contribute to the onset, maintenance, and recurrence of psychiatric symptoms. Objective assessments using polysomnography and actigraphy have revealed disorderspecific patterns, such as increased REM density in depression and schizophrenia, prolonged sleep latency in anxiety and personality disorders, and circadian rhythm disturbances in bipolar disorder and autism spectrum disorder. Pharmacologic treatments, particularly psychotropics, often affect sleep architecture, sometimes exacerbating underlying sleep disorders like obstructive sleep apnea or sleeprelated movement disorders. Nonpharmacological approaches, notably cognitive behavioral therapy for insomnia (CBTI), show promise in improving both sleep and psychiatric outcomes. Emerging interventions tailored to specific disorders, such as CBTI for bipolar disorder or imagery rehearsal therapy for PTSDrelated nightmares, are highlighted. Routine sleep assessment in psychiatric settings and integrated treatment approaches that address both psychiatric symptoms and cooccurring sleep dysfunction are required. Ultimately, understanding and treating sleep disturbances is essential for improving quality of life and longterm recovery in individuals with psychiatric illness.