Circadian irregularity in schizophrenia and familial risk: a comparative study

BACKGROUND: Sleep-related characteristics in schizophrenia patients and circadian rhythms in the etiology and course of schizophrenia continue to be investigated. This study aims to compare chronotype characteristics in schizophrenia patients, their unaffected siblings as a familial/genetic risk group and healthy controls. METHODS: The study was conducted with 171 individuals, including 56 schizophrenia patients, 56 siblings, 59 controls. Structured Clinical Interview for DSM-5, Munich Chronotype Questionnaire(MCQ) were applied to all participants, Brief Psychiatric Rating Scale, Calgary Scale for Depression in Schizophrenia were applied to the patient group, and Patient Health Questionnaire-9 was applied to the sibling and control groups. RESULTS: The corrected midsleep on free days of the three groups calculated according to MCQ are: patients 4:32 ± 1:55; siblings 4:31 ± 1:22; controls 4:36 ± 1:01. No statistically significant difference was found between the three groups in terms of corrrected sleep midpoint means, radian value means, and chronotype distributions calculated using MCQ (respectively; p > 0.952, p = 0.934, p = 0.376). Retrospective evaluation of the premorbid period showed that the morningness type was more common and the intermediate type was less common in the schizophrenia group compared to the control group. The sibling group showed a distribution between these two groups (p = 0.023). While the mean radian values ​​for the mid-sleep points did not differ between the groups, a significant difference was found in terms of variance (schizophrenia: 0.119; sibling: 0.062; control: 0.036, p < 0.001). The variance of premorbid sleep midpoints radians was also found to be higher compared to the control group (schizophrenia: 0.1730; control: 0.0732, p = 0.001). The midpoint of sleep shifted to earlier hours with increasing age, and tended to shift to later hours with daily screen time, daily coffee consumption, and evening cigarette use (p < 0.05). CONCLUSIONS: These findings suggest that schizophrenia patients have endogenous difficulties in regulating circadian rhythms and that their siblings may have similar, but milder, irregularities. Circadian irregularities seen in schizophrenia patients may be an independent phenomenon of this disorder and may be present the onset of the disease. So this situation should be taken into account in the evaluation of individuals at risk.