3.1 General
Much of violence risk assessment in psychiatry is invisible, carried out routinely by clinicians in the course of their work. Violence risk is one of many considerations that inform a range of decisions from admission to hospital to the most appropriate form of outpatient care. Even when risk of harm to others becomes a focus of the doctor’s interaction with his or her patient, the principles underlying its assessment are the same as those underlying psychiatric practice more generally. An evaluation will be based on the result of taking a history and examining a patient’s mental state.
Accurate assessment depends on the availability of accurate information. This will usually include information obtained from collateral sources, such as medical records, informants and, where the police have been involved, police reports. Assessments carried out at the point of admission to hospital are of necessity often limited in these respects, and unresolved issues of risk, like other clinical issues unresolved at the time the patient enters the hospital, require continued attention in the course of an admission. Additional investigation, including psychological testing, may be required. Particularly with regard to specialist areas of practice, such as assessing the risk of sexual offending, it may be appropriate to ask colleagues and specialist services to consult on the case.
Sometimes, psychiatric assessments of violence risk are conducted to address an explicit question, such as whether the risk to others can be managed in a community setting. In such instances the most useful assessments are usually conducted in response to questions that are clear, specific and clinically focused. People’s mental states change, as do the circumstances in which they find themselves, and assessments that focus on the short term are less likely to be rendered irrelevant by subsequent changes in either of these. The most helpful risk assessments not only describe the situation at the time of the evaluation but what can be done to mitigate risk in the future.
3.2 Correlation and Cause in Assessing Risk
Psychiatrists assessing violence risk evaluate cases in several different ways. First, they look for the presence of factors associated with violence. Some of what clinicians know about the correlates of violence derives from empirical research. While empirical research can increase confidence that a risk factor is associated with violence, it cannot be relied upon to identify all such risk factors. To be confirmed empirically, risk factors have to occur frequently enough to be studied and be capable of being measured. Some reported risk factors, such as Capgras phenomena (
12-
14), are uncommon while others concern interpersonal relationships whose complexity renders them difficult to define for research purposes (
15).
The correlation-based data available in the criminological and psychiatric literature suggest that risk factors for violence act differently in some respects among people with mental disorders compared with the general population. The tendency for violent acts to be conducted by men is still present but less strong, first offenses occur later and the likelihood of acting violently does not fall off so rapidly with advancing age (
16). The protective effect of stable relationships may also be less (
17,
18), particularly where someone’s social and occupational functioning is poor (
19). In other respects, however, the correlates of violent offending in the general population apply also to people who suffer from mental disorders (
20).
Thus crimes of violence are more often committed by younger males and recidivism for violent crimes is less than for property crime. Substance abuse is associated with both violent and nonviolent crime. The more serious the crime, generally speaking, the lower the risk of repetition, although the incapacitating effects of long sentences make direct comparisons of reoffending rates problematic. First offenders, on average, fare better, in terms of reconviction, following conviction than do people with extensive criminal records. Unemployment, living in a high-crime neighborhood and having antisocial peers all add substantially to risk (
20).
The last 40 years has seen the publication of empirical studies describing in greater detail than was available previously the risk factors that apply in particular settings and patient groups. Those that have been identified in general psychiatric settings (
17,
21,
22) are listed in
Table 1.
In other settings additional factors may be important. In emergency rooms and inpatient units an aggressive attributional style (hostile, suspicious, or believing others intend harm), command hallucinations to harm others and a poor therapeutic alliance have been implicated (
23-
25). Some paraphilias are risk factors for sexual offending (
26).
A second way in which psychiatrists assess risk, in addition to looking for risk factors, is by combining their understanding of the patient’s personality, symptoms and environment with their understanding of the likely causes of violence. Where someone suffers from persecutory delusions that concern their spouse, for instance, there will usually be available no empirical data from research conducted on samples of similar patients demonstrating a correlation between continued cohabitation and violence. Yet the clinician’s understanding of the likely causes of violence may still allow him or her to conclude that continued cohabitation presents a risk (
27).
Pollock offers one description of the processes involved:
The skillful clinician assessing dangerous behavior formulates and tests a series of clinical hypotheses to define patterns of violence in the individual’s history. Once defined, these patterns can be applied to the explanation and prediction of violence in that individual (28 at 105).
Approaches to risk assessment based on explanations of this type seem to rely heavily on induction, because they require the clinician to draw conclusions about the future from past observations. Future conditions will never exactly mimic the conditions in which behavior has occurred in the past, yet the circumstances of other episodes of violence, whether in the patient’s case or more generally, will usually be relevant and sometimes be critical. Notwithstanding the uncertainty inherent in this process, one task of risk assessment is to determine the relevance of past patterns.
Clinicians trying to work out what might cause future violence are guided also by the understanding of patterns of behavior that they develop in their training and through clinical practice (
29,
30). Claims that “causal” ways of thinking are better than correlation-based ones at predicting rare events (
31) have not been confirmed by empirical research. Instead, the persistence of causal approaches when clinicians think about risk may relate to the fact that many of the other judgments required in medicine are causation-based also: establishing why someone has symptoms, for instance, or deciding which further investigations are needed to complete an evaluation. Because clinical practice requires each of these judgments to be integrated into a single plan, it may be that clinicians find it helpful to use the same causal heuristic in assessing risk that they use in other aspects of their work.
3.3 Structure in Risk Assessment
Both correlation- and cause-based approaches to risk assessment can be structured. Structure can be provided in more than one way. Actuarial instruments such as the VRAG (
32) formalize the process by which the simultaneous presence of more than one correlate of violence increases the perception of risk. They do this by rating variables such as poor school adjustment and alcohol problems and combining these mathematically to generate an overall score or category. A different type of instrument relies on “structured professional judgment.” The HCR-20 (
33), for instance, encourages the clinician to assess the relevance of a list of pre-identified variables but also to take into account other information, including factors he or she considers unique to the case, before allocating a case to a risk category.
Structured approaches are sometimes treated as a distinct category within risk assessment but are better seen as differing from unstructured methods in degree rather than kind (
34). Even in the absence of a structured instrument, clinicians use structures derived from their professional training to take a history and to examine the patient. Some of these structures appear in practice guidelines. Structure offers the same advantages to risk assessment that it offers to other areas of clinical practice. It is a means of integrating and communicating information (
35). It can be a useful
aide memoir, particularly when the clinical question being addressed is unusual (some risk factors apply particularly to sex offences, for instance: see page 3, column 2). Learning how to structure the clinical approach is a key aspect of clinical training (
36).
Examples of structured instruments for the assessment of violence risk are listed in
Table 2 (a).
The time taken to complete these instruments varies with the amount of material reviewed. Further information on their use is provided in the references cited in the Table.
Although the majority of research on the Static 99 has been in relation to sexual offending, all of the instruments in
Table 2 have been tested in a range of settings and found to predict violence in a range of patient groups. Different instruments have been developed to help assess risk in particular treatment settings, such as inpatient units (
50), and specific patient groups (
51). The number and scope of these structured approaches to risk assessment has increased substantially since the APA Task Force Report, “Clinical Aspects of the Violent Individual,” was published in 1974 (
52,
53). One recent review counted 126 (
54).
When structured approaches combine those variables into risk assessment instruments they have the benefit of allowing the evaluator to make the results of his or her evaluation transparent: with the necessary information on how items were completed and combined the reader can see how the conclusions were arrived at. Early suggestions that structured approaches are also more accurate (
55,
56) were initially criticized on the grounds that many of the predictions included in early comparisons did not concern violence (
57). Subsequent research seemed to confirm, however, that structured approaches perform better, on average, than unstructured ones when violence risk is looked at separately (
58), at least when the follow-up period covers months or years. Recent reviews have reached the same conclusion (
53).
This combination of transparency and empirically demonstrated accuracy has contributed to an increased use of structured instruments since 1974, particularly by specialist services. The degree to which structured approaches will be used in the future will ultimately depend on whether they benefit care. Several issues warrant further investigation. First, the evaluations of risk that are required in hospital and outpatient practice frequently concern hours, days or weeks. There is a shortage of empirical data to indicate whether the long term accuracy of structured methods is matched by their accuracy over these shorter periods (
59). Some of the reasons for the relative lack of research in this area are discussed in Section 4.
Second, researchers seek to limit the amount of missing data in follow-up studies. Clinicians have little option but to work with a lot of it. Their response to not having a collateral account of someone’s criminal record, for instance, is presumably unstructured, yet the performance of clinicians in the emergency room seems not to be very different from that of structured instruments (
60,
61). We do not yet know to what extent the performance of structured instruments is adversely affected by the absence of some of the information necessary to complete the items. Third, although the number of validations has grown rapidly in recent years, a clinician will not always have available an instrument that has been shown to be effective in measuring risk in the relevant patient group.
Fourth, events can make the results of using a rating scale no-longer applicable. Physical incapacity (the so-called “broken leg exception” (
62) to using a score as an indicator of risk) is an unusual, though often quoted, example. More common events, such as placement in a supervised setting, can be equally important. Finally, structured instruments generate a risk category (typically, low, medium and high) or a score. Clinical risk assessments address aspects of clinical management, for instance whether someone’s violence risk is sufficiently well managed for them to move to a supported apartment or whether it requires that they be admitted to the hospital. There is not yet available a tested and reliable means by which a score can be applied to decisions such as these. The process is further complicated by the fact that placement decisions are usually influenced by many factors, not just risk. Not all services and not all neighborhoods have the resources to support the same type of psychiatric provision, making the treatment implications of a particular score or category still more difficult to describe consistently.