The research question was how the characteristics of aggressive events (AE) in hospitalized psychiatric patients differ with respect to the previous duration of hospitalization. A retrospective study was conducted at the Psychiatric Hospital "Sveti Ivan" on the data from the hospital records of AE recorded in the period from January 1, 2015 until December 31, 2019. The main outcome was the type of AE where heteroaggression, verbal aggression, destruction of things and other ADs were distinguished. The main independent variable was the time from admission to AD in days. During the monitored period in the Psychiatric Hospital "Sveti Ivan" 89 AE were recorded. There was a difference in the time from admission to a psychiatric institution to the commission of an particular AD. Heteroaggressions and verbal aggressions occur earlier in the course of hospitalization than the destruction of things and other ADs. The median (IKR) time from admission to a heteroaggressive event or verbal aggression was 3 (1-11) days while the median time to destruction of things was 7 (1-12) and to other AD 8 (3-13) days. Based on this research, but also other AD studies in psychiatric institutions, it seems that AD risk assessments should include the time from admission, ie the duration of hospitalization, and that such risk assessments should be repeated several times and the treatment adjusted according to these results.