Introduction

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Serious acts of violence committed by people with mental illness are statistically rare events.¹ Efforts of community services to prevent violence by the small subgroup at risk may be limited by the lack of effectiveness of standard treatment interventions, inadequate attention to clinical factors associated with violencefor example, drug misuse and poor engagement and treatment adherence by patientsand the difficulty of altering risk associated with impoverished and dangerous living environments. ^{2 3} Fragmentation between services compounds the difficulties.

The care programme approach was introduced, partly to address this fragmentation, after several killings by people with severe mental illness were much reported in the media.⁴ The key elements are assessment of need and risk, development of a care plan, nomination of a responsible key worker, and regular review. Case management incorporates these principles, with the key worker providing direct care and also organising the delivery of a range of other services tailored to each patient's individual needs. Intensive case management emphasises small caseloads (10-15 patients per case manager), with increased intensity of contact.

Surprisingly, no study has specifically examined the effect on violence of increasing the intensity of treatment in the community. We assessed whether intensive case management reduced the prevalence of violence in comparison with standard case management.

	Methods

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Study population
The participants in the trial were recruited as part of the UK700 randomised controlled trial of the efficacy of intensive case management in patients with psychosis.⁵ Recruitment took place between February 1994 and April 1996 in four inner city mental health services. Inclusion criteria were age between 18 and 65, a diagnosis of psychosis according to research diagnostic criteria,⁶ and at least two inpatient admissions for psychotic illness, with one in the previous two years. Patients with a primary diagnosis of substance misuse or organic brain damage were excluded.

Intervention
Intensive case management was compared with standard care for two years. Intensive case managers had caseloads of 10-15 patients, whereas standard case managers had 30 or more patients. Case managers were mostly community psychiatric nurses but could also be psychologists, occupational therapists, mental health support workers, or social workers.

Assignment
After giving written informed consent and being interviewed, patients were individually randomised to intensive case management or standard care. Randomisation was stratified by centre, ethnic origin, and source of recruitment.

Outcomes and follow up
Participants were interviewed by independent researchers at baseline and two years after randomisation. Researchers were senior trainee psychiatrists or psychology graduates who were totally independent of clinical care but, for safety purposes, were not always masked to treatment allocation. For the current study the outcome of interest was physical assault in the two years of the trial.

Power calculation and statistical analysis
The trial with 350 patients randomised to each group would be able to detect a 20% reduction in total violence in the intensive case management group as statistically significant at the 5% level with a high probability (power >80%). We compared treatment groups by using the ² test. We used logistic regression to perform univariate and multivariate analyses to identify predictors of assault during the two years of the trial.

	Results

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Recruitment
Eighty per cent of patients approached agreed to participate (figure). Details of the sociodemographic and clinical features of the participants in the UK700 trial have been described in detail elsewhere.⁵

View larger version (37K): [in this window] [in a new window]   Flowchart of trial

Intervention
Patients in the intensive case management group received more than twice as much care as control patients, with a mean of 4.41 events per 30 days compared with 1.94 in the standard arm. The mean duration of face to face contacts was 40.6 (SD 0.3) minutes in the intensive management group and 37.4 (24.8) minutes in the standard group. Patients managed intensively had significantly more of each type of event apart from failed contacts and received significantly more contacts related to the criminal justice system, engagement, finance, and medicationall variables that might influence the prevalence of violent behaviour.

Prevalence of violence
Information on assault was available for all patients from at least one data source. During the two years of the trial 80 (23%) of the intervention group and 78 (22%) of the control group committed assault, representing no significant difference (relative risk 1.03 (95% confidence interval 0.72 to 1.46), ²=0.048, P=0.86). Identified risk factors for violence included previous violence, younger age, drug misuse, victimisation, and learning difficulties (table). After adjustment for these factors, the difference in prevalence of violence between the groups remained non-significant.

	Discussion

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In the largest randomised trial to date comparing intensive case management with standard care in psychosis, no significant reduction in violence was found. Risk factors for violence included previous violence, drug misuse, younger age, and victimisation, confirming the results of previous studies in psychotic patients. ^{12 13} Violence was also associated with a history of learning difficulties, a factor previously identified in non-psychotic populations.¹⁴

Strengths and weaknesses of the study
Different methods for measuring violence can produce very different prevalences.¹⁵ The recent use of multiple combined measures, as in this study, has highlighted the limitations of most previous studies, which relied on a single source. Our results support the observation that self report methods consistently produce a higher frequency of violence than use of other records (see full version on BMJ 's website).¹⁶

Prevalence of violent behaviour
The finding that 22% of patients committed assault over the two year period is of concern but concurs with previous work. Studies indicate that between 10% and 40% of patients commit assault before admission to hospital, and the MacArthur risk assessment study found that 28% of discharged psychiatric patients committed at least one violent act within a year of discharge. ^{17 18}

Implications of the study
Despite the lack of empirical studies on the effect of increasing the intensity of treatment in the community on violence in general psychiatric or forensic populations, research in the United States is now focusing on the effect of combining community treatment with legally enforceable interventions to reduce violence. A recent study, with some important limitations in its methods, found that outpatient commitment (enforced community treatment) for longer than six months combined with regular services resulted in a significant reduction in community violence in severely mentally ill patients at risk of violence. Neither outpatient commitment nor regular services alone was effective.²⁶ Similar legislation for compulsory community treatment in England and Wales has recently been proposed in a government white paper.²⁷ Future research may have the challenging task of evaluating the effectiveness of combining specific clinical interventions within or without a protective legal framework.

	Acknowledgments

The UK700 Group is a collaborative study team involving four clinical centres. Manchester: Tom Butler, Francis Creed, Janelle Fraser, Peter Huxley, Nicholas Tarrier, Theresa Tattan. King's/Maudsley, London: Tom Fahy, Karyna Gilvarry, Kwame McKenzie, Robin Murray, Jim van Os, Elizabeth Walsh. St Mary's/St Charles' Hospitals, London: John Green, Anna Higgitt, Elizabeth van Horn, Donal Leddy, Catherine Manley, Patricia Thornton, Peter Tyrer. St George's Hospital, London: Rob Bale, Tom Burns, Matthew Fiander, Kate Harvey, Andy Kent, Chiara Samele. York (health economics): Sarah Byford, David Torgerson, Ken Wright. London School of Hygiene and Tropical Medicine (statistical centre): Simon Thompson, Ian White.

	Footnotes

Editorial by Steinert

Funding: EW was funded by a Wellcome Training Fellowship. The UK700 trial was funded by grants from the Department of Health and NHS research and development programme.

Competing interests: None declared.

The full version of this paper appears on the BMJ's website

	References

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(Accepted 23 July 2001)