Elsevier

The Lancet

Volume 358, Issue 9297, 8 December 2001, Pages 1955-1959
The Lancet

Articles
Detention of people with dangerous severe personality disorders: a systematic review

https://doi.org/10.1016/S0140-6736(01)06962-8Get rights and content

Summary

Background

UK government proposals to reduce the risks posed by people with “dangerous” severe personality disorders (DSPD) include a new legal framework for indeterminate detention. We aimed to establish the degree to which those operating the framework will be able to predict which people will act violently in the future.

Methods

We reviewed published reports in which the accuracy of a clinical judgment or a statistically derived rating of dangerousness was validated by its use to predict the violent behaviour of adults in the community. We calculated the sensitivity and specificity of the procedures used by every study. We then applied these sensitivities and specificities to the purported base rates of violence in people with DSPD.

Findings

23 studies fulfilled the criteria, and for 21 of these the sensitivity and specificity of the procedures used by the investigators could be calculated. Using the average positive predictive power of these procedures, six people would have to be detained to prevent one violent act. Making predictions over shorter periods did not improve their accuracy.

Interpretation

In practice, the number of people that need to be detained is likely to be higher than we reported. Differences between populations in respect of which predictions are being made and the population on which an instrument was validated will reduce the accuracy of that instrument. Not all of the necessary information will always be available.

Introduction

In July, 1999, the UK Home Office and the Department of Health published Managing Dangerous People With Severe Personality Disorder.1 The document outlines two sets of proposals for reduction of the risk posed by people with “dangerous” severe personality disorders (DSPD). Under the first, the present framework of criminal and mental health law would be changed so that people with severe personality disorders would not be released from prison or hospital if they presented a risk to the public. Under the second, a new legal framework would provide powers for the indeterminate detention of people with DSPD in criminal and civil proceedings. Legislative plans were published in 2000.2

The 1999 document makes reference to three groups of people with DSPD: those leaving secure hospitals, those leaving prison, and those in the community. No definition of DSPD is provided and it is not a recognised term in psychiatry or psychology; it seems to consist of people with a diagnosis of antisocial personality disorder who carry, in addition, a diagnosis of at least one other type of personality disorder and who have six or more unspecified risk factors. The document estimates that 400 male patients in secure hospitals fall into the category, along with 1422 adult male sentenced prisoners and 300–600 people in the community.

The proposals have provoked debate on the morality of preventively detaining people who have not been convicted of an offence. This debate cannot be resolved by research. It is linked, however, to an empirical question. To what extent is it possible to identify those who will behave violently in the future? Only by an extreme deontological standard is preventive detention unacceptable in all circumstances. For most people the argument is, in part, utilitarian. The degree to which preventive detention of the unconvicted, and detention of the convicted for longer than would presently be the case, is acceptable is related to the degree to which it is possible accurately to identify those who will, and those who will not, behave violently. We aimed to establish how many patients would have to be detained to avert one incident of serious violence.

Section snippets

Methods

The criteria for inclusion were based on those used by Mossman.3 We searched Medline and PsycINFO databases electronically with the Index Medicus medical subject headings predict and violence, and predict and dangerous.

We included only studies that presented original data, that appeared in peer-reviewed journals since 1970, and in which the accuracy of a clinical judgment or a statistically derived rating of dangerousness was validated by use in prediction of violent behaviour of adults in the

Results

The results are shown in the table and—for the 21 studies in which figures for sensitivity and specificity could be obtained—the figure. Numbers of people refer to the number for whom there was sufficient information for analysis.

The indices of effectiveness range from −0·10 to 1 · 1; the overall mean is 0·58 (95% CI 0·42 to 0·73). Studies in which predictions are made over shorter periods do not report greater effectiveness. The mean index of effectiveness of studies which used clinical

Discussion

The studies differed in terms of the frequency and nature of mental disorder. Although these differences might not affect the results, if and when a definition of DSPD becomes available it may be possible to test whether those studies that used a similar patient group achieved a better level of accuracy. The studies we have examined also used different definitions of violence. It may be that certain forms are more easily predicted. For example, it could be that published reports examining

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