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BACKGROUND Though schizophrenia is associated with substantial psychiatric comorbidity, data pertaining to multiple comorbid psychiatric disorders among individuals with schizophrenia is missing. Furthermore, despite abundant research indicating that the course of schizophrenia is characterized by relapses, often leading to psychiatric emergency room visits and consequent hospitalizations, data regarding the association between different comorbid psychiatric diagnoses among schizophrenia patients, and these hospitalization-related factors is lacking. The aim of this study was to describe the number and types of comorbid psychiatric diagnoses of inpatients diagnosed with schizophrenia, and to explore whether these are associated with hospitalization-related factors. METHODS Registry data from the years 1997-2017 was analyzed from a large psychiatric hospital database. We compared the annual mean number of psychiatric emergency room visits and hospitalizations, as well as mean length of hospitalizations, among individuals with schizophrenia and no additional psychiatric diagnosis, to those with one or more comorbid psychiatric diagnoses. Furthermore, we compared these hospitalization-related based on the different types of the comorbid diagnoses. RESULTS Among inpatient individuals with schizophrenia, the greater the number of comorbid psychiatric diagnoses, the higher the increase in number of emergency room visits and hospitalizations, as well as in the mean length of hospitalizations. Furthermore, all comorbid psychiatric disorders explored were found to be associated with an increase in the mentioned hospital-related factors. Such diagnoses include substance use disorders, bipolar, personality and depressive disorders, which were the most common disorders associated with schizophrenia. CONCLUSIONS Comorbid psychiatric disorders among inpatients with schizophrenia are associated with greater utilization of hospital-related services. These comorbid disorders should be addressed in the assessment and treatment of patients suffering from schizophrenia.