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Prevalence of Aggressive or Violent Behaviour in Thai Patients with Schizophrenia: a Cross-Sectional Study.


Patients with schizophrenia may experience distress, delusion, hallucination, and disorganised speech and behaviour. The rates of aggressive or violent behaviours and criminal offences have been reported to be higher among patients with schizophrenia than in the general population. (1-9) People with schizophrenia are 20-times more likely than the general population to commit homicide. (10) Approximately 1 in 600 patients with schizophrenia commit homicide prior to treatment, and the rate of homicide after antipsychotic treatment is about one in 10 000 patients per year. (11)

Aggressive or violent behaviour in patients with schizophrenia may be a response to psychotic delusions (especially paranoid or persecutory delusions), hallucinations, or misperceptions, and therefore a psychotic form of self-defense. (12) Factors associated with aggressive or violent behaviours in patients with schizophrenia include severity of psychotic symptoms, personality dimensions, substance abuse, and mentalising abilities, (13,14) whereas sociodemographic risk factors include economic deprivation (15) and social living status. (16)

There are few studies on factors associated with aggressive development, especially in Asian patients with schizophrenia. This study aimed to identify factors associated with aggressive or violent behaviour in Thai patients with schizophrenia.


The study was approved by the Ethics Committee of Faculty of Medicine, Chiang Mai University (EC/MEDCMU- PSY-2556-01814) and the Ethics Committee of Suan Prung Psychiatric Hospital (EC/SPPH-17-2556). Informed consent was obtained from each participant. This cross-sectional study was conducted in the largest mental health hospital in northern Thailand. All inpatients with schizophrenia aged [greater than or equal to]18 years admitted between January and November 2014 were screened for eligibility. Those who were diagnosed with any type of schizophrenia and received any treatment (antipsychotic drugs, electroconvulsive therapy, and/or supportive therapies) were included. Those who did not provide informed consent, refused to cooperate, or had other psychiatric disorders (schizoaffective disorder, bipolar disorder, major depressive disorder with psychotic feature, or delusional disorder) were excluded, as were those with severe medical conditions such as severe alcohol withdrawal syndrome or temporal lobe epilepsy.

Baseline interviews were conducted by a psychiatrist and psychiatric nurses. Demographic data such as sex, age, educational level, marital status, occupation, income, duration and type of schizophrenia, and treatment were collected. Patient characteristics were collected from the patients themselves, their relatives, and medical records. The diagnosis of schizophrenia was based on the Mini-International Neuropsychiatric Interview, Thai Version 5.0.0, a short structured diagnostic interview, and the DSM IV-TR, whereas the severity of comorbidities was measured using the Charlson comorbidity index. (17)

Violence includes threats and verbal aggression, aggression against property, self-harming behaviour, and physical aggression. (11,18) The psychosocial aspects potentially leading to aggressive or violent behaviour include relationships between patients and others (neighbours, co-workers, or family members), public reprimand or blame, forced treatment or medication, criticism from others (family members, relatives, friends, neighbours, or co-workers), and home and community environments. (11) Accessibility to weapons and toxic chemicals was evaluated; higher scores indicated higher risk of accessing weapons/toxic chemicals. History of being charged by the police with a criminal offence or convicted in a court of a criminal offence was collected.

In a previous study, the prevalence of aggressive or violent behaviour in patients with schizophrenia admitted to remand prison was 6.1% (166/2743). (3) The sample size required to make calculations with a 95% confidence interval was calculated as 88 patients; therefore, we planned to recruit 200 patients. To identify factors associated with aggressive or violent behaviour, violent and non-violent patients were compared using t-test or the Mann-Whitney U test (for continuous variables) and Fisher's exact test or [chi square] test (for categorical variables). A binary logistic regression model was applied to identify predictors of aggressive or violent behaviour. Significant independent variables (p < 0.05) and covariates (p < 0.20) at the bivariate level were included. All statistical analyses were carried out using SPSS (Windows version 22; IBM Corp, Armonk [NY], US)


Of the 230 patients with schizophrenia screened, 23 were excluded owing to incomplete data, and 207 (162 men and 45 women) with a mean age of 38.7 [+ or -] 10.3 years were included (Figure). Of the 207 patients, 67.6% were single; they had a mean of 7.7 [+ or -] 3.8 years of education; 36.7% were unemployed; and therefore, their income was low. 142 (68.6 %) had been diagnosed with paranoid schizophrenia and had the condition for a mean of 7.0 [+ or -] 7.7 years; 63 (30.4%) were treated with electroconvulsive therapy; and 35 (16.9%) had suicidal risk. Only 16 (7.7%) of patients had aggressive or violent behaviour, including verbal aggression (n = 7), physical aggression (n = 5), and aggression against property (n = 4). Nonetheless, only 2 (12.5%) of them had been charged by the police.

Violent and non-violent patients were comparable in terms of sex, age, years of schooling, marital status, occupation, personal and household income, and duration and type of schizophrenia. However, the weapon score was higher in violent patients (p < 0.05, Table 1). The binary logistic regression analysis showed that the weapon score was the only significant predictor of violence (adjusted [R.sup.2] = 0.172, standard error of the estimate = 0.034, Wald = 4.197, Table 2).


In the present study, only 16 (7.7%) patients with schizophrenia had aggressive or violent behaviour, mostly verbal aggression. Of them, only 2 (12.5%) were charged by the police for violent offenses. However, neither of those was convicted in court. The risk of aggressive or violent behaviour was significantly higher in patients with higher access to weapons.

The prevalence of violent offences is greater in patients with schizophrenia than in normal populations. A case-control study reported that the lifetime and 5-year prevalence of violent offence in patients with schizophrenia after the first admission was 8.2% and 3.0%, respectively, compared with 1.8% and 0.4% in controls. (1) Similarly, a meta-analysis found that 9.9% of patients with schizophrenia and other psychotic conditions were violent, compared with 1.6% of the general population. (10)

Substance use disorder is associated with aggressive or violent behaviour in patients with schizophrenia, (1,10,19-23) as are personality co-morbidities, particularly antisocial personality trait or disorder. (24,25) However, in Japanese patients with schizophrenia, violent behaviour is related to schizophrenic symptoms rather than antisocial traits or substance use disorder. (13) Similarly, the present study showed no association of substance use disorder or personality traits or disorders with schizophrenia in our patients. Rather, aggressive or violent behaviour may be caused by several factors before, during, and after periods of active illness and may be affected by cultural and racial diversity. (1,13)

The present study had some limitations. The sample size was small; a larger sample is needed to confirm these findings. All patients with schizophrenia were hospitalised, and their factors for developing aggressive or violent behaviour may differ from those of other non-hospitalised patients or patients with other psychotic conditions. Thus, the findings should only be generalised with caution. Cultural differences may influence the development of aggressive or violent behaviour in Thai patients with schizophrenia, and the findings may not be generalisable to other populations. Some patients who had committed acts of severe violence or homicide were imprisoned, and this may have also affected the prevalence of aggressive or violent behaviour that we found.


Thai patients with schizophrenia who had higher access to weapons were more likely to have aggressive or violent behaviour. Routine screening for access to weapons in clinical settings and adequate treatment of psychotic symptoms may reduce the incidence of aggressive or violent behaviour and violent offences.


This work was supported by the Faculty of Medicine, Chiang Mai University (046/2557) and Chiang Mai University (04/2562).


Narong Maneeton has received travel reimbursement from Lundbeck and Pfizer. Benchalak Maneeton has been an advisory board member of Pfizer and received honoraria and/or travel reimbursement from Lundbeck, Servier, and Pfizer. Natthanan Jaiyen, Pakapan Woottiluk, and Wajana Khemawichanurat report no conflicts of interest.


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Narong Maneeton, MD, FRCPsychT, Department of Psychiatry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.

Benchalak Maneeton, MD, FRCPsychT, Department of Psychiatry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand.

Natthanan Jaiyen, MS (forensic), The Graduate School Chiang Mai University, Chiang Mai University, Chiang Mai, Thailand

Pakapan Woottiluk, APPMHN, MNS, RN, Psychiatric Nursing Division, Faculty of Nursing, Chiang Mai University, Chiang Mai, Thailand

Wajana Khemawichanurat, MD, FRCPsychT, Suan Prung Psychiatric Hospital, Chiang Mai, Thailand

Address for correspondence: Dr Benchalak Maneeton, Department of Psychiatry, Faculty of Medicine, Chiang Mai University, Chiang Mai, Thailand. Email:

Submitted: 20 December 2017; Accepted: 30 May 2018
Table 1. Demographic data of patients with schizophrenia.

Factor                                   Non-violent
                                        (n = 191) (*)

 Male                                 151 (72.9)
 Female                                40 (19.4)
Age, y                                 38.4 [+ or -] 10.2
Years of schooling                      7.7 [+ or -] 3.7
Educational level
 Uneducated                            16 (7.7)
 1-6 years                             81 (39.1)
 7-9 years                             51 (24.6)
 10-12 years                           29 (14.0)
 [greater than or equal to]13 years    14 (6.8)
Marital status
 Married                               31 (15.0)
 Single                               130 (62.8)
 Divorced/separated                    25 (12.1)
 Widow                                  5 (2.4)
 Unemployed                            68 (32.9)
 Employee                              74 (35.7)
 Owner                                 11 (5.3)
 Government officer                     1 (0.5)
 Agriculture                           29 (14.0)
 Monk                                   7 (3.4)
 Student                                1 (0.5)
Annual personal                      1643 [+ or -] 3092
income, US$
Annual household                     3320 [+ or -] 4556
income, US$
Duration of                             7.2 [+ or -] 7.7
schizophrenia, y
Received                               61 (29.5)
Having suicidal risk                   34 (16.4)
Type of schizophrenia
 Paranoid                             133 (64.3)
 Disorganized                           2 (1.0)
 Catatonic                              1 (0.5)
 Undifferentiated                      54 (26.1)
 Unspecified                            1 (0.5)
Charlson comorbidity                    0.1 [+ or -] 1.5
index score
Nicotine use                           71 (34.3)
Alcohol use                            17 (8.2)
Amphetamine use                         6 (2.9)
Poor relationships with                46 (22.2)
neighborhood(s) or
Poor relationships with                39 (18.8)
family member(s)
Patients reprimanded or                37 (17.9)
blamed in public
Patients often subjected               52 (25.1)
to forced treatment
Patients subjected to                  54 (26.1)
forced medication
Patients criticised by                 39 (18.8)
family member(s) or
Poor housing and home                  31 (15.0)
Improper environmental                 29 (14.0)
Weapon score                           18.0 [+ or -] 8.7

Factor                                    Violent          p Value
                                        (n = 16) (*)

 Male                                  12 (5.8)             0.751
 Female                                 4 (1.9)
Age, y                                 42.3 [+ or -] 11.2   0.201
Years of schooling                      7.0 [+ or -] 4.7    0.571
Educational level                                           0.118
 Uneducated                             3 (1.4)
 1-6 years                              6 (2.9)
 7-9 years                              1 (0.5)
 10-12 years                            4 (1.9)
 [greater than or equal to]13 years     2 (1.0)
Marital status                                              0.619
 Married                                3 (1.4)
 Single                                10 (4.8)
 Divorced/separated                     2 (1.0)
 Widow                                  1 (0.5)
Occupation                                                  0.885
 Unemployed                             8 (3.9)
 Employee                               5 (2.4)
 Owner                                  1 (0.5)
 Government officer                     0 (0)
 Agriculture                            2 (1.0)
 Monk                                   0 (0)
 Student                                0 (0)
Annual personal                      1616 [+ or -]1765      0.715
income, US$
Annual household                     2443 [+ or -] 2873     0.314
income, US$
Duration of                             5.3 [+ or -] 6.7    0.350
schizophrenia, y
Received                                2 (1.0)             0.156
Having suicidal risk                    1 (0.5)             0.318
Type of schizophrenia                                       0.463
 Paranoid                               9 (4.3)
 Disorganized                           0 (0)
 Catatonic                              0 (0)
 Undifferentiated                       7 (3.4)
 Unspecified                            0 (0)
Charlson comorbidity                    0.3 [+ or -] 1.0    0.190
index score
Nicotine use                            5 (2.4)             0.637
Alcohol use                             0 (0)               0.372
Amphetamine use                         2 (1.0)             0.119
Poor relationships with                 7 (3.4)             0.131
neighborhood(s) or
Poor relationships with                 2 (1.0)             0.744
family member(s)
Patients reprimanded or                 3 (1.4)             1.000
blamed in public
Patients often subjected                7 (3.4)             0.162
to forced treatment
Patients subjected to                   7 (3.4)             0.252
forced medication
Patients criticised by                  5 (2.4)             0.341
family member(s) or
Poor housing and home                   3 (1.4)             0.731
Improper environmental                  4 (1.9)             0.293
Weapon score                           23.6 [+ or -] 8.1    0.021

(*) Data are presented as mean [+ or -] standard deviation or No. (%)
of participants.

Table 2. Binary logistic regression analysis of predictors for
aggression/violence in patients with schizophrenia.

Co-variable                     [beta]  Standard   Wald

Uneducated                       0.761   0.745     1.044
Electroconvulsive therapy       -1.002   0.804     1.554
Charlson comorbidity index       0.078   0.139     0.316
Amphetamine use                  1.394   0.964     2.093
Poor relationships               0.980   0.613     2.553
Patients with forced treatment   0.486   0.599     0.659
Weapon score                     0.070   0.034     4.197
Constant                        -4.451   0.923    23.258

Co-variable                       Odds ratio (95%     p Value
                                confidence interval)

Uneducated                      2.140 (0.497-9.211)    0.307
Electroconvulsive therapy       0.367 (0.076-1.774)    0.213
Charlson comorbidity index      1.081 (0.824-1.419)    0.574
Amphetamine use                 4.032 (0.610-26.670)   0.148
Poor relationships              2.664 (0.801-8.858)    0.110
Patients with forced treatment  1.626 (0.503-5.256)    0.417
Weapon score                    1.073 (1.003-1.148)    0.041
Constant                        0.012                  0.000
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Title Annotation:Original Article
Author:Maneeton, Narong; Maneeton, Benchalak; Jaiyen, Natthanan; Woottiluk, Pakapan; Khemawichanurat, Wajan
Publication:East Asian Archives of Psychiatry
Article Type:Clinical report
Geographic Code:9THAI
Date:Sep 1, 2019
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