Association Between Specific Insomnia Symptoms and Aggression in Chinese Patients with Chronic Schizophrenia: A...

Aggression is a significant issue in schizophrenia, with insomnia identified as a modifiable risk factor. However, research often treats insomnia as a single construct, neglecting potential differences among its symptoms: difficulty initiating sleep (DIS), difficulty maintaining sleep (DMS), and early morning awakening (EMA). This study examined these distinct associations in a large sample of Chinese patients with chronic schizophrenia.

A total of 702 inpatients with chronic schizophrenia was approached and screened. Among them, 31 were excluded due to missing data, resulting in a final sample size of 671. Aggression was assessed with the Modified Overt Aggression Scale, insomnia symptoms with the Insomnia Severity Index, and psychopathology with the Positive and Negative Syndrome Scale (PANSS). Logistic regression models examined associations between insomnia symptoms and aggression, controlling for theory-driven set of demographic and clinical variables identified from the literature as potential confounders (age, gender, illness duration, PANSS factor scores, antipsychotic dosage, clozapine use, polypharmacy, and sleep medication usage).

The prevalence of aggression, DIS, DMS, and EMA were as follows: 14.6% (n=98), 14.2% (n=95), 11.3% (n=76), and 9.6% (n=64). One-fifth of the patients used sleep medication. Unadjusted analyses linked all three insomnia symptoms to increased aggression risk, with DIS showing the strongest association (Crude odds ratio =4.18, 95% CI=2.55-6.86, p<0.001). After full adjustment, only DIS remained independently associated (Adjusted odds ratio=3.81, 95% CI=1.77-8.21, p<0.001). Further analysis revealed DIS rather than DMS or EMA was uniquely linked to all aggression domains: verbal, property, auto-, and physical aggression.

DIS, rather than other insomnia symptoms, shows a consistent and independent association with multiple forms of aggression, highlighting its clinical significance in managing chronic schizophrenia. Clinical assessment should therefore differentiate between insomnia symptoms, and longitudinal and interventional studies are needed to confirm this association and explore its therapeutic implications.