Aggression in drug-dependent in-patients

AIMS AND METHOD

Associations have been reported between aggression and psychoactive substance use, and a link with violence has been demonstratedin community samples. This study aimed to assess the prevalenceand nature of aggressive incidents and to examine the factorsassociated with violence in a specialist substance misuse treatmentunit. Data were collected about assaults, aggressive patientsand the object of their aggression during a 12-month period.

RESULTS

Eighteen of 165 patients admitted during this period were involvedin aggressive incidents. Patients dependent on more than onesubstance were significantly more aggressive than other categoriesof drug users. Past history of assaultive behaviour, youngerage group and shorter duration of use were also significantlyassociated with incidents of aggression. Socio-demographicvariables such as gender, marital and employment status were poor predictors of aggression.

CONCLUSIONS

The incidence of serious violence in this substance misuse treatmentunit was low when compared with other psychiatric units. Thefindings suggest that there are differences in levels of aggressionamong the various types of drug users. The study reinforcesthe need for an accurate drug history in order to improve thequality of risk assessment.

Introduction

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Introduction

The ability to predict the likelihood of aggression is an importantpart of psychiatric practice, and an understanding of the factorsthat may increase the risk of assault is useful in clinicalpractice. Research conducted with in-patient samples has shownincreased rates of violence associated with schizophrenia (Tardiff & Sweillam, 1982;McNiel et al, 1988; Binder & McNiel, 1995),organic mental disorders (Tardiff & Sweillam, 1982; Hodgkinson et al, 1985), mania (McNiel et al, 1988; Binder & McNiel, 1995),personality disorders and mental retardation (Tardiff & Sweillam, 1982; Hodgkinson et al, 1985). Associationshave been reported between in-patient aggression and psychoactivesubstance use (Blomhoff et al, 1990), and a link with violencehas been demonstrated in community samples (Swanson et al, 1990; Tardiff et al, 1997). Dual diagnosis of a severe mentalillness and a substance misuse disorder has a highly significantassociation with aggression (Scott et al, 1998). There isevidence that the type of drug used may be important, with stimulant drugs such as cocaine and amphetamine increasing the risk ofviolence (Miles et al, 2003).

Although there is a general agreement that substance misuseincreases the risk of in-patient aggression, much of the researchsupporting this has been conducted in psychiatric hospitalsand the results may not be generalisable to specialist substancemisuse treatment units. To date there has been no study ofthe incidence of aggression in such units, and the characteristicsof aggressive, drug-dependent patients are not clear. As aresult, clinicians are forced to take important decisions aboutrisk management in substance misuse in-patient settings withoutadequate knowledge of factors predicting the risk of aggression.In this study we aimed to determine the rates of aggression among drug-dependent in-patients during their admission, andto describe the nature of violent episodes in terms of targetand severity of injury. In doing so, we aimed to clarify thedemographic and diagnostic categories of patients that presenta greater risk of aggressive incidents.

Method

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Method

The Addictive Behaviours Centre is a 16-bedded in-patient unitproviding a detoxification service for alcohol and other substancesfor Birmingham and neighbouring areas in the West Midlands.All patients are admitted voluntarily and enter into a treatmentcontract at the time of admission, one of the clauses of whichdefines acceptable behaviour on the unit. Patients are told that verbal or physical aggression, racist comments or possessionof offensive weapons are prohibited, and that a written warningwill be administered should such an episode take place. Allsuch incidents result in the completion of an incident reportform, and any repetition of the behaviour leads to premature discharge from the unit.

This study retrospectively reviewed all incident report formscompleted between April 1999 and March 2000. Each form wasanalysed and information extracted according to a data collectionpro forma. In addition, the clinical notes of all patientsadmitted during the study period were examined in order toidentify any unreported incidents. For the purpose of our study,an ‘incident’ was defined as any act of physicalor verbal aggression with a hostile intent by a patient towardsa fellow patient, a member of staff or property. The severityof assault was rated on a six-point scale devised in a previousstudy (Miller et al, 1993):

no injury (verbal threat only)
no injury (property damage)
unlikely injury (push or pull)
minor injury (scratch orslap)
moderate injury (punch, bite or kick)
considerableinjury (sustained assault)

Demographic data were also collected on all patients, as wellas diagnostic information based on the ICD-10 classificationsystem (World Health Organization, 1992). The characteristicsof those involved in aggressive incidents were compared withthose of others who had not been aggressive; all data analyseswere performed using the Statistical Package for the Social Sciences, version 10.0. Statistical significance was establishedusing the ${chi}$ ² test for categorical data, with Fisher’sexact test employed when appropriate, and the Mann-WhitneyU test for continuous data; a P value of less than 0.05 wasconsidered significant.

Results

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Results

Of the 165 patients admitted during the study period, most weremale (73%), under 50 years old (89%), White (83%) and unemployed(90%). The most frequent substances of dependence were alcohol(54%) and opiates (28%), with multiple drug dependence (15%)also prominent. Nearly a third (31%) of people in the samplehad an additional ICD-10 psychiatric diagnosis (with depressionbeing the most common), and two-thirds had a forensic history(a history of contact with the judicial system for any criminalbehaviour). A total of 18 patients were classified as havingbeen aggressive during their inpatient stay. A majority ofthe incidents (67%) were verbal threats only, and there wasno serious incident during the study period. Physical aggression(i.e. contact assault) was rare, occurring in just 4% of alladmissions. Staff and fellow patients were the victims in eightincidents each and property was damaged in two incidents (Table 1).

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Table 1. The nature of aggressive incidents and the victims

The aggressive patients were significantly younger than thenon-aggressive group (mean age 42.7 years v. 37.8 years, Z=-2.058, P=0.04) and had a shorter duration of substance use (14.1 years v.19.8 years, Z=-2.186, P=0.029). Patients with polydrug dependencywere significantly more aggressive than all the other patientscombined ( ${chi}$ ²=9.63, P=0.006), and those dependent on alcoholwere significantly less aggressive than all other groups ( ${chi}$ ²=5.566,P=0.018). There was no statistically significant differencebetween the aggressive and non-aggressive groups of patientsin terms of gender, race, employment status and the presenceor absence of additional diagnosis (Table 2). A previous forensichistory was not associated with aggression, although therewas some evidence that a past history of violence either inthe hospital or in the community was more common in the aggressive group (56% v. 32%, ${chi}$ ²=3.944, P=0.047).

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Table 2. Comparison of aggressive and non-aggressive patients

Discussion

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Discussion

In this study the prevalence of contact assaults (those involvingmore than verbal aggression) was 4%, which is lower than the7-10% found in studies in psychiatric units (Miller et al, 1993). This low rate may be explained by the fact that thesample contained a large proportion of patients who were motivatedto change their behaviour, and none of the patients was detainedunder the Mental Health Act 1983. In addition, the clear clinicalboundaries set by the treatment contract imposed on everyoneadmitted to the unit probably contributed to the lower levelof assaults. Younger patients were more likely to be aggressivethan older patients, a finding in agreement with results fromother studies (Tardiff & Sweillam, 1982; James et al,1990). The statistical analysis did not suggest that comorbiditywith other psychiatric disorders was associated with aggressiveepisodes, but it was noticeable that three out of four peoplewith schizophrenia were involved in recorded incidents.

The study showed that people using more than one illegal drugwere significantly more likely to be aggressive than others.Such patients undergo a complicated withdrawal process, andmay experience a range of physical and psychological withdrawalsymptoms. For example, the adrenergic discharge associatedwith opiate withdrawal may lead to irritability and thus to aggression. Four out of seven polydrug users who were involvedin incidents of aggression during their admission were alsodependent on cocaine, which in itself has been associated withaggressive behaviour (Tardiff et al, 1997). Other factorsindependent of the withdrawal process predispose this groupto aggression. Some authors have suggested a complex inter-relationshipbetween substance type, personality, life events and socioculturalfactors (Fagan, 1990). People using more than one illegal drugtend to have a range of other medical and psychosocial problems (Schuckit, 2000), and this may in turn cause difficultiesin their management. Our experience suggests that this groupof patients is particularly challenging to manage, as it canbe difficult to negotiate an appropriate rate and type of detoxification.There is a need for very clear treatment contracts before admissionto prevent misconceptions regarding the purpose of admission.

Obvious limitations to our study are the retrospective natureof the data collection and the reliance on recorded incidents.The latter is likely to have led to an underestimate of thenumber of aggressive incidents, particularly those not involvingphysical aggression. The study numbers were small and the resultsmay not be generalisable to other units. However, we feel thatthe results are helpful in suggesting risk factors for aggressive incidents in substance misuse in-patient treatment services.Professionals working in all in-patient psychiatric servicesshould be aware of the need to assess risk carefully, and payparticular attention to groups such as younger patients withpolydrug use who may need increased support in order to prevent such aggressive incidents.

Acknowledgments

We are grateful to Dr Syed Haque for his advice on statisticsand to Mrs Anne Farmer, Mrs Elizabeth Cooksey and Mrs JoanneWilliams for their help with collecting and organising data.

References

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