Prevalence and Correlates of Aggression and Hostility in Hospitalized Schizophrenic Patients

Introduction

Numerous studies have shown the increasing rates of aggressive behavior among persons with mental disorders compared with the general population (e.g., Bjorkly, 2002; Dunn et al., 2007; Eronen, Hakola, & Tiihonen, 1996; Link, Stueve, & Phelan, 1998). Individuals with schizophrenia in particular are reported to be engaged in the acts of aggression that are more frequent and more severe than those with other psychiatric illnesses (Fazel & Grann, 2006; Fazel, Langstrom, Hjern, Grann, & Lichtenstein, 2009; Laajasalo & Hakkanen, 2005; Silver, Goodman, Knoll, Isakov, & Modai, 2005; Soyka, Graz, Bottlender, Dirschedl, & Schoech, 2007; Swanson, Holzer, Ganju, & Jono, 1990; Swanson et al., 2006; Walsh, Buchanan, & Fathy, 2001; Witt, Van Dorn, & Fazel, 2013). The proportion of society’s total violent crime that can be attributed to schizophrenia is low, as is to be expected considering the fact that people with schizophrenia comprise about 1% of the general population (Eronen et al., 1996; Hodgins, Mednick, Brennan, Schulsinger, & Engberg, 1996; McNamara & Findling, 2008; Swanson, 1994). In contrast to previous data (Foley et al., 2005), recent studies suggest that clinical factors may be a significant concern in those with a mental disorder (Gray, Taylor, & Snowden, 2011; O’Shea, Picchioni, Mason, Sugarman, & Dickens, 2014). Studies to date are undermined by the use of varying definitions of aggression and a paucity of validated instruments to assess aggressive acts committed by persons with schizophrenia (Serper, 2011).

Socio-demographic factors have been examined in relation to aggressive behavior in schizophrenic patients, and the results from studies have been contradictory. Some studies have reported that men with schizophrenia commit acts of aggression more frequently than women (Bitter, Basson, & Dossenbach, 2005; Mann, 1998), and some studies have found no gender differences (Volavka, 1999). Similarly, some authors have concluded that aggressive patients are younger than non-aggressive patients; however, others found contradictory results (Bitter, Basson, & Dossenbach, 2005; Bitter, Czobor, Dossenbach, & Volavka, 2005; Resnick, 1998).

Several studies that have looked at the correlation between psychopathology and aggression have found a positive relationship between aggression and positive symptoms of schizophrenia (e.g., Fresán et al., 2005; Joyal, Putkonen, Paavola, & Tiihonen, 2004; Swanson et al., 2006; Verna, Poon, Subramaniam, & Chong, 2005; Witt et al., 2013). Others found that aggressive behavior was not correlated with positive symptoms, when the effects of hostility are controlled (e.g., Appelbaum, Robbins, & Monahan, 2000; Junginger, Parks-Levy, & McGuire, 1998; Volavka, 2013). Others using the Violence Risk Assessment Scheme (HCR-20) consistently report that active psychotic symptoms, rather than the positive/negative nature of symptoms per se, are predictive of violent recidivism in schizophrenic patients (Gray et al., 2011; O’Shea et al., 2014).

The aim of this study was to examine the prevalence of aggression and hostility in patients with schizophrenia at hospital admission and to identify the association between aggression/hostility and certain socio-demographic and clinical factors in these patients.

Method

The study sample consisted of patients with Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR; American Psychiatric Association [APA], 2000) diagnose of schizophrenia who were admitted to the Clinic for Psychiatry in Novi Sad, Serbia during 2012 and 2013. Following the approval by the Ethics Committee of the Clinical Centre Vojvodina, a written informed consent was obtained from all patients after they were given a full explanation of the nature of the study. Exclusion criteria included presence of major medical illness and psychiatric comorbidities (including active substance misuse and personality disorders).

We assessed the symptoms using the Positive and Negative Syndrome Scale (PANSS; Kay, Fiszbein, & Opler, 1987) and aggression using the Modified Overt Aggression Scale (MOAS; Kay, Wolkenfeld, & Murrill, 1988). The MOAS is a version of the Overt Aggression Scale (OAS) devised by Yudofsky, Silver, Jackson, Endicott, and Williams (1986), and modified by Kay et al. (Kay et al., 1988). This scale consists of four subscales: verbal aggression, aggression against property, autoaggression, and aggression toward others. Each participant was rated on a scale between zero (no aggression) and four (maximum score) on each subscale. The subscale scores were weighted as described by Kay et al. (1988). To calculate the total MOAS score, verbal aggression was multiplied by 1, aggression against property score was multiplied by 2, autoaggression score was multiplied by 3, and aggression toward others score was multiplied by 4. The sum of these measured scores is the MOAS total score. We used the MOAS to assess all incidents of aggression recorded as occurring in the week prior to each patient’s admission in the hospital.

We analyzed the data using SPSS and used Student t test, Mann−Whitney test, chi-square test, and Pearson correlation.

Results

One thousand thirty-three patients with a DSM-IV-TR diagnosis of schizophrenia were admitted to the Clinic of Psychiatry during the observed period. Five hundred fifty-four patients (53.6%) were men. The age of patients ranged from 18 to 78 years, while the average age was 40 and the median 39 years. Three hundred twenty-three individuals (31.3%) demonstrated aggression and hostility, which was defined as a score ≥3 on the MOAS, and a score ≥3 on P7 item of the PANSS that reflects Hostility.

After applying the exclusion criteria, the sample was reduced to 110 individuals. In that reduced sample, 67 patients (60.9%) were men and their age ranged from 19 to 58 years, while the average age was 37 years. There was no difference between the two groups in terms of gender (χ² = 2.12, p > .05). However, aggressive and hostile patients were significantly younger compared with the whole sample (Mann-Whitney U = −2.5, p < .05). Clinically, the sample was moderately symptomatic, according to the PANSS and MOAS (Table 1, Table 2).

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Table 1.

Descriptive Statistics of the PANSS.

Variable	Minimum	Maximum	Average Value	SD
Total PANSS	52	120	86.52	15.04
Positive Scale a	14	34	24.26	4.03
Negative Scale	7	34	20.99	5.96
General psychopathology	24	62	41.26	7.42
Hostility item (P7)	3	7	4.64	1.37

Note. PANSS = Positive and Negative Syndrome Scale.

a

With hostility.

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Table 2.

Descriptive Statistics of the MOAS.

Variable	Minimum	Maximum	Average Value	SD
Total MOAS	3	24	9.35	5.78
Verbal aggression	1	4	2.38	0.99
Aggression toward objects	0	8	2.87	1.7
Autoaggression	0	12	0.9	2.39
Physical aggression	0	12	3.2	4.15

Note. Weighted results. MOAS = Modified Overt Aggression Scale.

There were no significant differences between the gender groups in terms of PANSS total score (p = .287), but statistical trends were evident between the genders on scores of the hostility item (p = .057), MOAS total score (p = .048), and aggression toward objects subscale of the MOAS score (p = .013). However, there was a clear difference between gender groups in terms of the physical aggression subscale of the MOAS (p = .006), with men showing significantly higher level of physical aggression (Table 3).

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Table 3.

Gender Differences in Terms of PANSS and MOAS Scores.

Variable	Men	Women	df	Student t Test	p
Positive Scale	24.83	23.37	108	1.88	.063
Negative Scale	21.53	20.14	108	1.2	.232
General psychopathology	41.37	41.09	108	0.192	.848
Total PANSS	87.75	84.6	108	1.07	.287
Hostility	4.84	4.33	108	1.92	.057
Verbal aggression	2.43	2.44	108	−0.5	.614
Aggression toward objects	3.19	2.37	108	2.53	.013
Autoaggression	0.63	0.13	108	−1.56	.135
Physical aggression	4.01	1.86	108	2.79	.006*
Total MOAS	10.22	8	108	2	.048

Note. Due to the use of the Bonferroni correction, significance level is at .006. PANSS = Positive and Negative Syndrome Scale; MOAS = Modified Overt Aggression Scale.

*

p < .01.

The results failed to find a statistical association between socio-demographic characteristics and PANSS or MOAS scores (Table 4). However, the level of hostility (measured by item P7 of the PANSS) is positively and strongly correlated with the level of aggression measured by MOAS (r = .77, p < .01). No significant association was found between hostility and other items of the PANSS positive scale, or with the total PANSS score. However, the PANSS hostility item demonstrated a small but significant negative correlation with PANSS negative subscale (r = −.21, p < .05). No statistical association was found between the level of aggression (measured by MOAS) and the total PANSS score. Similarly, no association was found between aggression levels on the MOAS and the PANSS positive subscale, with the hostility item omitted. The level of aggression, as the level of hostility, was negatively correlated with the PANSS negative subscale (r = −.25, p < .01).

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Table 4.

Association Between Socio-Demographic and Clinical Characteristics of the Sample.

	1	2	3	4	5	6
1. Age	—
2. Number of hospitalizations	.49*	—
3. Duration of disorder	.87*	.5*	—
4. PANSS	.02	.15	.00	—
5. Hostility item	.00	−.04	−.3	−.1	—
6. MOAS	.08	.03	.08	−.03	.77*	—

Note. PANSS = Positive and Negative Syndrome Scale; MOAS = Modified Overt Aggression Scale.

*

p < .01.

Discussion

We used the MOAS to assess multiple dimensions of aggression, including verbal aggression, aggression against property, autoaggression, and aggression toward others. The MOAS is a well-validated, reliable scale that we used to assess aggression (Kay et al., 1988). MOAS assessments were performed retrospectively in addition to using prospectively collected clinical and socio-demographic data as possible predictors of aggression and hostility.

The overall incidence of aggression and hostility in patients diagnosed with schizophrenia was 31%, which is similar to that reported by many authors (e.g., Arango, Barba, Gonzalez-Salvador, & Ordonez, 1999; Chukwujekwu & Stanley, 2011; Craig, 1982; McNiel & Binder, 1986; Rossi et al., 1985; Tardiff, Marzuk, Leon, Portera, & Weiner, 1997; Tardiff & Sweillman, 1980). We did not find significant gender differences between aggressive and non-aggressive hospitalized patients diagnosed with schizophrenia. There was no association of aggression and hostility with the gender in the group of aggressive and hostile patients. However, it was found that male patients showed higher scores on the MOAS subscale of physical aggression. We must note that Bonferroni corrections, used to assess the significance of gender differences, are exceedingly stringent, and given the preliminary nature of this line of investigation, some leeway might be accorded so that observed differences such as between males and females in aggression toward objects (p = .013) may not be regarded as simply due to chance and dismissed out of hand in future research.

It was found that the group with reported aggression and hostility was significantly younger than the group of all hospitalized schizophrenic patients. However, when we observed only the group with reported aggression and hostility, there was no correlation between their age, the serial number of hospitalization, and the length of the illness with the level of their aggression and hostility. The principal reason why the study did not find any socio-demographic correlates of aggression may well be that the selected predictors have no intrinsic relationship with aggression per se, beyond a general notion that younger males tend to be more aggressive. Socio-demographic factors would certainly have greater significance for predicting aggression if we observed only certain types of aggression, according to the neurobiologically based aggression typology.

Similar to many other studies, we found that socio-demographic variables (such as gender, age, duration of illness, and number of hospitalizations) are poor at predicting aggression in schizophrenic patients (e.g., Borum, Swartz, & Swanson, 1996; Volavka, 2002). Some authors even suggest that the influence of socio-demographic factors is even lower in hospitalized patients than psychiatric patients in general (e.g., Volavka, 1999). However, we did not include some potentially interesting or frankly causal socio-demographic variables that could lead to different results.

We found that there is a strong association between the level of aggression and the level of hostility in our sample. Assaultive behavior is included in the PANSS definitions of hostility, and therefore, it is not surprising that an association could be found between these two variables (Volavka & Citrome, 2011).

Like many authors, we did not find that the level of aggression was significantly associated with clinical characteristic (such as PANSS scores) in hospitalized schizophrenic patients (e.g., Appelbaum et al., 2000; Joyal et al., 2004; Junginger et al., 1998; Verna et al., 2005; Volavka, 2013; Witt et al., 2013).

However, interestingly, there was a weak negative association between the level of aggression and the PANSS negative scale, and this result is consistent with the results of other studies (e.g., Fazel, Grann, Carlstrom, Lichtenstein, & Langstrom, 2009; Swanson et al., 2006).

This study was not designed to characterize the nature of aggression, beyond recurrent aggression that was registered by MOAS. However, there is a theoretically derived three-factor model for conceptualizing aggression of psychiatric inpatients. According to this model, the aggression can be irritable, instrumental, or delusion-based defensive (Urheim et al., 2014). If we could discriminate between specific types of aggression, predictions could be more precisely focused, and the treatment recommendations and risk management could be better directed.

Failure to consider types of aggression likely led to negative results in this study. If we have considered only the delusion-based defensive type of aggression, this would certainly lead to a significant association of this type of aggression with positive symptoms of schizophrenia. To the extent that the aggression is increased by positive psychotic symptoms, the crucial role of symptom management becomes clear, and pharmacological treatments are the principal tools to manage aggression (Levi, Nussbaum, & Rich, 2010; Urheim et al., 2014). However, impulsive aggression, being the more commonly reported type in individuals with major mental disorder such as schizophrenia, might have shown very little difference between positive and negative symptoms of schizophrenia (Nolan et al., 2003). However, the risk of aggression could be increased by many nonclinical variables, which suggests that risk management must include a focus on the whole person in the community.

Our study had other limitations. First, these cross-sectional data cannot demonstrate causal connections between variables; rather, they show statistical associations, which may, or may not, be consistent with a causal relationship. Second, the data about acts of aggression were gathered in a retrospective manner that could have led to underreporting of the aggressive incidents and the severity of aggression. Third, participants in this study may not be representative of all persons with schizophrenia. Our sample consisted of a group of hospitalized schizophrenic patients, and one of the reasons for hospitalization likely included aggressive behavior, regardless of other clinical indicators. Finally, we did not take into account the history of patient’s aggressive behavior which is, according to the literature, one of the strongest predictors of aggressive behavior (Klassen & O’Connor, 1988; Meehan et al., 2006).

Conclusion

Aggressive behavior carries a high human and social cost. The likelihood that some individuals with schizophrenia may commit assaultive acts is a significant limitation in the process whose purpose is to normalize mental health services within the community.

In conclusion, socio-demographic variables and the included clinical characteristics were not good predictors of aggressive behavior in hospitalized schizophrenic patients. Nevertheless, the results of our study contribute to an understanding of the epidemiology of aggression in a well-defined cohort of schizophrenic patients without the confounding effects of substance misuse.

Future studies that examine the relationships between type of aggression and specific mental illness symptoms will add to our understanding of the relationship between aggression and mental illness.