Study design and sample
The current study is a retrospective analysis of the characteristics of aggressive events perpetrated by adult (i.e., 18–65 years) patients with a psychotic disorder during their hospitalization in a psychiatric ward of the Department of Psychiatry, Psychotherapy and Psychosomatics of the University Hospital of Psychiatry Zurich. For all patients admitted between January 2018 and December 2021, we reviewed the clinical incident system and extracted their demographic and clinical data from the electronic medical record.
The study was conducted in accordance with the Declaration of Helsinki, and approved by the Ethics Committee of the Canton of Zurich (BASEC-Nr. 2021 − 01246). Patient consent was waived due to approval by the Ethics Committee of the Canton of Zurich.
The University Hospital of Psychiatry Zurich is a public hospital with a service mandate for psychiatric care covering a mixed urban and rural region of approximately 500,000 inhabitants. It offers in- and outpatient treatment for adults with a psychiatric disorder. Since the definition and operationalization of violence and aggression in the medical field are heterogeneous, we decided to use the definition as it is anchored in Swiss legislation (illegal actions with damage to objects or threats or physical injuries to other people). Furthermore, due to legal and liability requirements, all such events are monitored and systematically reported to a clinical incident system.
Demographics, diagnoses, and measurement instruments
For analysis, we included basic demographic data (i.e., age, sex, highest education, and housing condition). Diagnoses were made using the WHO ICD-10 diagnostic criteria; we included the Health of the Nation Outcome Scale (HoNOS); and the Staff Observation Aggression Scale (SOAS-R) in its revised version.
The main diagnosis was made during hospitalization according to the ICD-10 diagnostic criteria by the treating physician or psychologist and confirmed by a board-certified psychiatrist. For the analysis, we included all diagnoses with psychotic features since these diagnoses exhibit a clear indication for the prescription of an antipsychotic drug. Therefore, diagnoses of interest included: schizophrenia (F20); delusional disorder (F22); brief psychotic disorder (F23); schizoaffective disorder (F25); mania with psychotic features (F30.2); and bipolar disorder with psychotic features, either manic (F31.2) or depressive (F31.5) episode. Existing comorbid diagnoses of substance use disorder were also made according to the ICD-10 criteria. (i.e. intoxication, harmful use, dependence or withdrawal). For the analysis the following substances were included alcohol use disorder (ICD-10: F10); opioid use disorder (ICD-10: F11); cannabis use disorder (ICD-10: F12); benzodiazepine use disorder (ICD-10: F13); cocaine use disorder (ICD-10: F14); and stimulant use disorder (ICD-10: F15).
The Health of the Nation Outcome Scales (HoNOS) is a measurement instrument used to assess the severity and treatment requirements of patients with a psychiatric disorder; it has become a widely used evaluation tool, and in some countries, it is a mandatory outcome measure. The HoNOS evaluates 12 domains covering behavior, symptomatology, impairment, and psychosocial functioning. Each item is rated on a five-point Likert scale from 0 (“no problem”) to 4 (“severe to very severe problem”). We evaluated the HoNOS at scale level (i.e., sum score ranging from 0 to 48) [
18‐
21]. Furthermore, we considered HoNOS items rated as three or four clinically significant and integral to the patient’s care plan [
21].
The Staff Observation Aggression Scale-Revised Version (SOAS-R) was developed to measure the nature and severity of aggressive events [
22]; it has become a widely used and validated tool for measuring inpatient aggression [
22,
23]. A detailed scoring system allows characterize and quantify the severity of an aggressive event [
24]. Therefore, events are rated in five domains, with several categories, each assigned a different grading. The maximum score in each domain is chosen, and a sum score builds- the SOAS-R ranges from 0 to 22 points. The severity of the event can be categorized as mild (0–7 points), moderate (8–15 points), and severe (12–22 points) [
25].
The first domain of the SOAS- R appraises whether there was a provocation leading to the aggressive event, it is scored from 0 to 2 points. A score of zero (“0”) indicates that the event was provoked through waiting, receiving help in daily activities, or the patients being denied something or provoked by other patients. A score of one (“1”) is given if there is no obvious or understandable provocation; a score of two (“2”) is given if the event is provoked through the request or instruction of the staff (e.g., requiring the patient to take medication).
The second domain rates the means used by the patient and can be scored from 0 to 3 points. A score of zero (“0”) indicates verbal aggression or threats. A score of one (“1”) is given if aggressive events involve the use of ordinary non-dangerous objects (e.g., furniture). A score of two (“2”) is given if there is bodily aggression (e.g., use of punch or kick). Finally, a score of three (“3”) is given if weapons, dangerous objects, or methods are used (e.g., knife, strangulation).
The third domain rates the target of aggression scored from 0 to 4 points. A score of zero (“0”) is given if there is no target of aggression. A score of one (“1”) is given if the target of aggression is an object (e.g., furniture). If the aggression involves other patients, a score of two (“2”) is given. A score of three (“3”) is given if the target of aggression are staff members (i.e., nurses, doctors, cleaning or security staff). Finally, a score of four is given if the targets of aggression are visitors or strangers to the ward (e.g., relatives, police).
The fourth domain rates the consequences for the victim(s); it is scored from 3 to 9 at three-point intervals (i.e., “0;” “3;” “6;” or “9”). Zero (“0) represents no harm or damage. Three (“3”), the object was damaged. Six (“6”) of the affected person(s) felt threatened. Finally, nine (“9”), there was an injury or pain requiring treatment.
The fifth and last domain rates the measures used to stop aggression, with a score between 0 and 4 in two-point intervals (i.e., “0;“ “2;“ or “4”). A score of zero (“0”) is given if talk down is sufficient and no other measures are necessary. A score of two (“2”) points is given if medication (peroral or parenteral) is given; or if the police have to be involved. Finally, a score of four (“4”) is given if the use of force is necessary for seclusion/isolation or restraint.
Medication
Antipsychotic medication was characterized according to their action on the dopamine D2 receptor affinity into two categories (see Table
1): Loose binding (e.g., olanzapine); or tight binding (e.g., risperidone) according to their dissociation constant Ki for the dopamine D2 receptor. If Ki is higher than the one of dopamine itself, the antipsychotic medication is classified as tight binding; and as loose binding, if their dissociation constant is lower than the one of dopamine itself [
16,
26,
27].
We assessed whether the patients were treated with an antipsychotic monotherapy or a combination of antipsychotics; or additionally also received an anxiolytic (i.e., benzodiazepines) or mood stabilizers (e.g., lithium, valproate). We calculated the Daily Defined Dose for each prescribed psychopharmacological agent and the Chlorpromazine Equivalents for the prescribed antipsychotic drugs. Only medication continuously taken in the past three days was considered. In case of changing doses, the higher dose was chosen. If patients took a combined antipsychotic therapy of a loose binding and tight binding antipsychotic they were grouped into the group of the agent with the higher CPZ-equivalent dose.
Table 1
Characteristics of antipsychotics prescribed to the sample population compared to dopamine
Loose binding or partial agonism
| | | |
Quetiapinea | 122 | 400 mg | 0.80 |
Clozapinea | 63 | 300 mg | 1.50 |
Cariprazinec | 18.0 | 3 mg | 100 |
Olanzapinea | 5.1 | 10 mg | 30 |
Amisulprideb | 1.8 | 400 mg | 0.86 |
Aripiprazoleb | 1.8 | 15 mg | 20.0 |
Tight binding
| | | |
Dopaminea | 1.75 | - | - |
Lurasidonec | 1.68 | 60 mg | 16 |
Paliperidoneb | 1.6 | 6 mg/2.5 mg | 66.7 |
Risperidonea | 1.1 | 5 mg/1.8 mg | 100 |
Haloperidola | 0.55 | 8 mg | 60.0 |
Zuclopenthixold | Comparable to Haloperidol | 30 mg/15 mg | 12 |