Despite public or media opinion, national studies have indicated that severe
mental illness does not independently predict future violent behavior, on
average, and is not a leading cause of violence in society. There is a statis-
tical association with various factors that do relate to violence (in anyone),
such as substance abuse and various personal, social and economic factors.
In fact, findings consistently indicate that it is many times more likely that
people diagnosed with a serious mental illness living in the community will be
the victims rather than the perpetrators of violence. In a study of individuals
diagnosed with "severe mental illness" living in a US inner-city area, a quarter
were found to have been victims of at least one violent crime over the course of
a year, a proportion eleven times higher than the inner-city average, and higher
in every category of crime including violent assaults and theft. People with a
diagnosis may find it more difficult to secure prosecutions, however, due in
part to prejudice and being seen as less credible.
However, there are some specific diagnoses, such as childhood conduct disorder
or adult antisocial personality disorder or psychopathy, which are defined by,
or are inherently associated with, conduct problems and violence. There are con-
flicting findings about the extent to which certain specific symptoms, notably
some kinds of psychosis (hallucinations or delusions) that can occur in dis-
orders such as schizophrenia, delusional disorder or mood disorder, are linked
to an increased risk of serious violence on average. The mediating factors of
violent acts, however, are most consistently found to be mainly socio-demograph-
ic and socio-economic factors such as being young, male, of lower socioeconomic
status and, in particular, substance abuse (including alcoholism) to which some
people may be particularly vulnerable.
High-profile cases have led to fears that serious crimes, such as homicide,
have increased due to deinstitutionalization, but the evidence does not support
this conclusion. Violence that does occur in relation to mental disorder
(against the mentally ill or by the mentally ill) typically occurs in the
context of complex social interactions, often in a family setting rather than
between strangers. It is also an issue in health care settings and the wider
community.
http://en.wikipedia.org/wiki/Mental_disorder#Perception_and_discrimination