The prevalence of insomnia disorder in inpatient psychiatric care

Sleep and mental health are intricately linked. Insomnia - defined as a dissatisfaction with sleep quantity or quality - is highly prevalent among patients with psychiatric disorders, exerting a negative impact on treatment outcome. However, the prevalence of insomnia on a symptom and diagnosis level (insomnia disorder) has not systematically been assessed in inpatient psychiatric care. The aim of this study was to systematically investigate the prevalence of insomnia symptoms and insomnia disorder according to Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria in inpatient psychiatric care. Comprehensive diagnostic interviews were conducted by trained clinicians in four German and two Swiss psychiatric hospitals. A total of 427 inpatients with psychiatric disorders across diagnostic groups were included (225 female, 200 male, 2 non-binary, mean age 40.8 ± 15.1 years, mean duration of psychiatric illness 8.6 ± 10.6 years). The prevalence of comorbid insomnia disorder, according to DSM-5 criteria, was 30.4% (95% CI [26.0%; 34.8%]). Additionally, 38.4% of patients (95% CI [33.8%; 43.0%]) reported regular insomnia symptoms but did not fulfill disorder criteria. Together, 68.8% of the sample (95% CI [66.4%; 73.2%]) were regularly affected by insomnia complaints. The prevalence of insomnia disorder was independent of age and diagnostic group, but significantly higher in women than in men (Fisher's exact test: p = 0.006, OR = 1.8, 95% CI [1.2; 2.8]). The current study is, to our knowledge, the first interview-based systematic investigation of the prevalence of insomnia disorder in inpatient psychiatric care. The high prevalence of around one third of patients is a call for action to implement a systematic diagnostic evaluation and state-of-the-art treatment of insomnia in routine psychiatric care. Of note, recent work demonstrates that adaptations of cognitive behavioral therapy for insomnia (CBT-I) - the first-line treatment according to guidelines-are feasible in inpatient psychiatric care. These interventions might have the potential to reduce the overprescription of hypnotic medication and to improve sleep and health.