Contents lists available at ScienceDirect International Journal of Law and Psychiatry journal homepage: www.elsevier.com/locate/ijlawpsy Psychological factors of aggressive behaviour in patients of forensic psychiatry wards with the diagnosis of schizophrenia Inga Markiewicz a, ⁎ , Anna Pilszyk a , Grzegorz Kudlak b a Department of Forensic Psychiatry, the Institute of Psychiatry and Neurology, Poland b Department of Forensic Psychiatry, the Institute of Psychiatry and Neurology, University of Warsaw, Poland ARTICLE INFO Keywords: Agression Violence Criminal acts Agressive behaviour Forensic patients ABSTRACT Scientific research shows that the likelihood of aggressive behaviour in people with mental disorders compared to healthy people is usually higher than among healthy people. Considering the social harmfulness of acts committed by persons suffering from schizophrenia, a thorough analysis of their conditions is recommended. The paper presents the results of research conducted by a team from the Forensic Psychiatry Clinic of the Institute of Psychiatry and Neurology (IPiN) in Warsaw regarding the psychological determinants of aggressive behaviour of people diagnosed with schizophrenia. The analysis covers selected demographic variables, per- sonality traits as well as the level and type of aggression presented, including previously undertaken violent behaviour. This article includes the results of studies on patients diagnosed with schizophrenia, interned in the Forensic Psychiatry Clinic of IPiN, as well as patients with schizophrenia (addicted and non-addicted) staying in general psychiatric wards. 1. Introduction Schizophrenia is a mental disorder which belongs to a group of endogenous psychoses. It is a chronic disease affecting approximately 1% of the population worldwide (Gałązka-Sobotka, Gryglewicz, Gierczyński, et al., 2015). It is one of the most debilitating disorders which, due to its nature and dynamics, significantly hinders the pa- tients' functional performance at the individual and social level. The symptoms of schizophrenia distort thinking, emotional reactions, be- haviour and, consequently, also the occupational and social functioning of the persons affected. Sometimes it happens that, while experiencing a psychotic episode, patients manifest aggressive behaviour towards others. There is no clear definition of aggression because it is a complex and ambiguous phenomenon. What connects the various co-occurring de- finitions of aggression is its classification as behaviour. It is widely believed that aggression is an intentional act the purpose of which is to cause injury, loss or pain to someone or something. Aggressive acts always involve acting in breach of legal norms and principles of peaceful coexistence in society. Psychology literature presents various concepts of aggression. Early models assumed that aggression was an innate tendency to react. Later, the relationship between frustration and aggression began to be noted. The authors of later psychological approaches developed this relationship into a more general model of negative affect and highlighted the role of cognitive factors and learning experiences (Krahe, 2006). The project adopted the concept of aggression developed by Buss and Perry (1992), who stated that im- pulsiveness had a large impact on the level of aggression as a perma- nent personality trait. The authors pointed to the relationship between impulsive behaviour and all components of aggression they mentioned: physical and verbal aggression, hostility and, especially, the level of anger. The issue of aggression, viewed in the context of law violations by persons with schizophrenia, relates, to a significant extent, to a psycho- pathological state, the aggravation of which may be associated with an aggression-prone behaviour. Research shows a link between schizo- phrenia and the increased risk of aggressive behaviour (Raja & Azzoni, 2005). Other research suggests that the persons affected are almost four times in greater risk of aggressive behaviour than those mentally healthy in the population (Swanson, Holzer, Ganju, & Jono, 1990; Volavka, 2002). The prevailing feeling in the literature is that violent behaviour more often occurs in patients who experience imperative hallucinations with commands to perform aggressive acts (Junginger & McGuire, 2001). Having regard to the intensity of all symptoms in schizophrenia, it was observed that aggressive patients are expected to present greater intensity of an overall psychopathology than patients https://doi.org/10.1016/j.ijlp.2020.101612 Received 21 April 2020; Received in revised form 6 July 2020; Accepted 15 July 2020 ⁎ Corresponding author at: 9 Sobieskiego Str., 02-957 Warsaw, Poland. E-mail address: ingam@ipin.edu.pl (I. Markiewicz). International Journal of Law and Psychiatry 72 (2020) 101612 0160-2527/ © 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/BY/4.0/). T