evaluates the relationship of mental illness
and violence by asking three questions: Are
the mentally ill violent? Are the mentally ill
at increased risk of violence? Are the public
at risk? Mental disorders are neither necessary
nor sufficient causes of violence. Major determinants
of violence continue to be socio-demographic
and economic factors. Substance abuse is a major
determinant of violence and this is true whether
it occurs in the context of a concurrent mental
illness or not. Therefore, early identification
and treatment of substance abuse problems, and
greater attention to the diagnosis and management
of concurrent substance abuse disorders among
seriously mentally ill, may be potential violence
prevention strategies. Members of the public
exaggerate both the strength of the association
between mental illness and violence and their
own personal risk. Finally, too little is known
about the social contextual determinants of
violence, but research supports the view the
mentally ill are more often victims than perpetrators
Are they more violent than people
without a mental illness? Are they a risk to
public safety? These questions have framed both
the scientific and the public debate surrounding
the relationship of violence to mental illness.
Unless otherwise stated, 'violence'
will refer to acts of physical violence against
others, since these are the most fear-inducing
for the public and the greatest determinants
of social stigma and discrimination. The term
'mental illness' will be reserved for non-substance
related disorders, usually major mental illnesses
such as schizophrenia or depression. Substance
related disorders and concurrent substance abuse
will be identified and discussed as separate
Are the mentally ill
Over time, there seems to have
been a progressive convergence of mental illness
and violence in day-to-day clinical practice.
From early declarations disavowing the competence
of mental health professionals to predict violence,
there has been a growing willingness on the
part of many mental health professionals to
predict and manage violent behaviour. With the
advent of actuarial risk assessment tools, violence
risk assessments are increasingly promoted as
core mental health skills: expected of mental
health practitioners, prized in courts of law
and correctional settings, and key aspects of
socially responsible clinical management (1,2).
Many psychiatrists, particularly
those working in emergency or acute care settings,
report direct experiences with violent behaviour
among the mentally ill. In Canada, for example,
where violence in the population is low relative
to most other countries, the majority of psychiatrists
are involved in the management and treatment
of violent behaviour, and 50% report having
been assaulted by a patient at least once (3).
However, clinical experiences with violence
are not representative of the behaviours of
the majority of mentally ill. Social changes
in the practice of psychiatry, particularly
the widespread adoption of the dangerousness
standard for civil commitment legislation, means
that only those with the highest risk of violence
receive treatment in acute care settings.
In fact, a serious limitation
of clinical explanations of violent and disruptive
behaviour is their focus on the attributes of
the mental illness and the mentally ill to the
exclusion of social and contextual factors that
interact to produce violence in clinical settings.
Even in treatment units with a similar clinical
mix and acuity, rates of aggressive behaviours
are known to differ dramatically, indicating
that mental illness is not a sufficient cause
for the occurrence of violence (4). Studies
that have examined the antecedents of aggressive
incidents in inpatient treatment units reveal
that the majority of incidents have important
social/structural antecedents such as ward atmosphere,
lack of clinical leadership, overcrowding, ward
restrictions, lack of activities, or poorly
structured activity transitions (4-6).
The public are no less accustomed
to 'experiencing' violence among the mentally
ill, although these experiences are mostly vicarious,
through movie depictions of crazed killers or
real life dramas played out with disturbing
frequency on the nightly news. Indeed, the global
reach of news ensures that the viewing public
will have a steady diet of real-life violence
linked to mental illness. The public most fear
violence that is random, senseless, and unpredictable
and they associate this with mental illness.
Indeed, they are more reassured to know that
someone was stabbed to death in a robbery, than
stabbed to death by a psychotic man (7). In
a series of surveys spanning several real-life
events in Germany, Angermeyer and Matschinger
(8) showed that the public's desire to maintain
social distance from the mentally ill increased
markedly after each publicized attack, never
returning to initial values. Further, these
incidents corresponded with increases in public
perceptions of the mentally ill as unpredictable
In some countries, such as
the United States, public opinion has become
quite sophisticated. The public judge the risk
of violence differently, depending on the diagnostic
group, with rankings that broadly correspond
to existing research findings. For example,
Pescosolido et al (9) surveyed the American
public (N=1,444) using standardized vignettes
to assess their views of mental illness and
treatment approaches. Respondents rated the
following groups as very or somewhat likely
of doing something violent to others: drug dependence
(87.3%), alcohol dependence (70.9%), schizophrenia
(60.9%), major depression (33.3%), and troubled
(16.8%). While the probability of violence was
universally overestimated, respondents correctly
ranked substance abusers among the highest risk
groups. Similarly, they significantly overestimated
the risk of violence among schizophrenia and
depression, but correctly identified these among
the lower ranked groups.
Public perceptions of the link
between mental illness and violence are central
to stigma and discrimination as people are more
likely to condone forced legal action and coerced
treatment when violence is at issue (9). Further,
the presumption of violence may also provide
a justification for bullying and otherwise victimizing
the mentally ill (10). High rates of victimization
among the mentally ill have been noted, although
this often goes unnoticed by clinicians and
undocumented in the clinical record. In a study
of current victimization among inpatients, for
example, 63% of those with a dating partner
reported physical victimization in the previous
year. For a quarter, the violence was serious,
involving hitting, punching, choking, being
beaten up, or being threatened with a knife
or gun. Forty-six percent of those who lived
with family members reported being physically
victimized in the previous year and 39% seriously
so. Three quarters of those reporting violence
from a dating partner retaliated, as did 59%
of those reporting violence from a family member
(11). In addition, many people with serious
mental illnesses are poor and live in dangerous
and impoverished neighbourhoods where they are
at higher risk of being victimized. A recent
study of criminal victimization of persons with
severe mental illness showed that 8.2% were
criminally victimized over a four month period,
much higher than the annual rate of violent
victimization of 3.1 for the general population
(12). A history of victimization and bullying
may predispose the mentally ill to react violently
when provoked (13).
Are the Mentally Ill
At Increased Risk of Violence?
Scientists are less interested
in the occurrence of isolated acts of violence
among those with a mental illness, and more
interested in whether the mentally ill commit
acts of violence with greater frequency or severity
than do their non-mentally ill counterparts.
Therefore, the question of whether the mentally
ill are at a higher-than-average risk of violence
is central to the scientific debate.
Definitive statements are difficult
to make and it is equally possible to find recent
literature supporting the conclusions that the
mentally ill are no more violent, they are as
violent, or they are more violent than their
nonmentally ill counterparts (14). Prior to
1980, the dominant view was that the mentally
ill were no more, and often less likely to be
violent. Crime and violence in the mentally
ill were associated with the same criminogenic
factors thought to determine crime and violence
in anyone else: factors such as gender, age,
poverty, or substance abuse. Any elevation in
rates of crime or violence among mentally ill
samples was attributed to the excess of these
factors. When they were statistically controlled,
the rates often equalized. However, although
the main risk factors for violence still remain
being young, male, single, or of lower socio-economic
status, several more recent studies have reported
a modest association between mental illness
and violence, even when these elements have
been controlled (1-2,7,13-16).
Because of the significant methodological
challenges faced by researchers in this field,
the nature of this association remains unclear.
For example, violence has been difficult to
measure directly, so that researchers have often
relied on official documentation or uncorroborated
self reports. The prevalence of violence has
been demonstrated to differ dramatically depending
on the source (17). Most samples have not been
representative of all mentally ill individuals,
but only of those with the highest risk of becoming
dangerous, such as those who are hospitalized
or arrested. Study designs have not always eliminated
individuals with a prior history of violence
(a major predictor of future violence), controlled
for co-morbid substance abuse, or clearly determined
the sequencing of events, thereby weakening
any causal arguments that might be made (14).
The MacArthur Violence Risk
Assessment Study recently completed in the United
States (1,18,19) has made a concerted effort
to address these problems, so it stands out
as the most sophisticated attempt to date to
disentangle these complex interrelationships.
Because they collected extensive follow-up data
on a large cohort of subjects (N=1,136), the
temporal sequencing of important events is clear.
Because they used multiple measures of violence,
including patient self-report, they have minimized
the information bias characterizing past work.
The innovative use of same-neighbour comparison
subjects eliminates confounding from broad environmental
influences such as socio-demographic or economic
factors that may have exaggerated differences
in past research.
In this study, the prevalence
of violence among those with a major mental
disorder who did not abuse substances was indistinguishable
from their non-substance abusing neighbourhood
controls. A concurrent substance abuse disorder
doubled the risk of violence. Those with schizophrenia
had the lowest occurrence of violence over the
course of the year (14.8%), compared to those
with a bipolar disorder (22.0%) or major depression
(28.5%). Delusions were not associated with
violence, even 'threat control override' delusions
that cause an individual to think that someone
is out to harm them or that someone can control
their thoughts. Previous cross-sectional studies
conducted in the United States (20,21) and Israel
(22,23) had linked threat-control override delusions
to an increased risk of violence.
The importance of substance
abuse as a risk factor for violence has been
well articulated in other studies. Consequently,
this may stand out as one of the robust clinical
findings in the field (24-28). Substance abuse
in the context of medication non-compliance
is a particularly volatile combination and poor
insight also may be a factor (25).
Are the Public at Risk?
It is important to keep in
mind that both serious violence and serious
mental disorder are rare events. Therefore,
it is difficult to judge the practical importance
of findings that may show an elevated risk of
violence among samples of mentally ill as they
tell us little about public risk.
One way of approaching this
issue is ask who are the most likely targets
of violence by the mentally ill: members of
the general public or members of their close
personal networks? Most recent studies suggest
that violent incidents among persons with serious
mental disorders are sparked by the conditions
of their social life, and by the nature and
quality of their closest social interactions
(29). In the MacArthur Violence Risk Assessment
Study (1), for example, the most likely targets
of violence were family members or friends (87%),
and the violence typically occurred in the home.
Discharged patients were less likely to target
complete strangers (10.7%) compared to their
community controls (22.2%). Similarly, in a
social network study that followed 169 people
with serious mental disorder over thirty months
(30), violence most frequently erupted in the
family when relationships were characterized
by mutual threat, hostility, and financial dependence;
when there was a diagnosis of schizophrenia
with concurrent substance abuse; and when outpatient
mental health services were used infrequently.
Of the over 3,000 social network members studied,
only 1.5% were ever targets of violent acts
A related question asks to what
extent do mentally ill contribute to the overall
prevalence of community violence. Using data
from the Epidemiologic Catchment Area studies
conducted in the United States, Swanson (31)
reported population attributable risks for self-reported
physical violence. Attributable risk refers
to the overall effect a factor has on the level
of violence in the population. For those with
a major mental disorder, the population attributable
risk was 4.3%, indicating that violence in the
community could be reduced by less than five
percent if major mental disorders could be eliminated.
The population attributable risk for those with
a substance abuse disorder was 34%, and for
those with a comorbid mental illness and substance
abuse disorder it was 5%. Therefore, by these
estimates, violence in the community might be
reduced by only 10% if both major mental disorders
and comorbid disorders were eliminated. However,
violence could be reduced by over a third if
substance abuse disorders were eliminated.
Using a similar approach, a
Canadian study asked what proportion of violent
crimes involving a police arrest and detention
could be attributed to people with a mental
disorder. They surveyed 1,151 newly detained
criminal offenders representing all individuals
incarcerated in a geographically defined area.
Three percent of the violent crimes accruing
to this sample were attributable to people with
major mental disorders, such as schizophrenia
or depression. An additional seven percent were
attributable to offenders with primary substance
abuse disorders. Therefore, if major mental
illness and substance disorder could be eliminated
from this population, the proportion of violent
crime would drop by about 10% (32).
Several general conclusions
are supported by this brief overview. First,
mental disorders are neither necessary, nor
sufficient causes of violence. The major determinants
of violence continue to be socio-demographic
and socio-economic factors such as being young,
male, and of lower socio-economic status.
Second, members of the public
undoubtedly exaggerate both the strength of
the relationship between major mental disorders
and violence, as well as their own personal
risk from the severely mentally ill. It is far
more likely that people with a serious mental
illness will be the victim of violence.
Third, substance abuse appears
to be a major determinant of violence and this
is true whether it occurs in the context of
a concurrent mental illness or not. Those with
substance disorders are major contributors to
community violence, perhaps accounting for as
much as a third of self-reported violent acts,
and seven out of every 10 crimes of violence
among mentally disordered offenders.
Finally, too much past research
has focused on the person with the mental illness,
rather than the nature of the social interchange
that led up to the violence. Consequently, we
know much less than we should about the nature
of these relationships and the contextual determinants
of violence, and much less than we should about
opportunities for primary prevention (30). Nevertheless,
current literature supports early identification
and treatment of substance abuse problems, and
greater attention to the diagnosis and management
of concurrent substance abuse disorders among
seriously mentally ill as potential violence
prevention strategies (25).
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