information here. Skip to the last few paragraphs if you don't want to
read some really negative science about schizophrenia.
Fazel, S. 2009, Schizophrenia and Violence: Systematic Review and
Meta-Analysis, PloS Medicine
http://www.plosmedicine.org/article/info:doi/10.1371/journal.pmed.1000120
The editor's summary is worth reading.
http://www.plosmedicine.org/article/info:doi%2F10.1371%2Fjournal.pmed.1000120#abstract2
Its not a pretty picture. Here's some snips.
"
For men with schizophrenia or other psychoses, the pooled odds ratio
(OR) from the relevant studies (which showed moderate heterogeneity) was
4.7, which was reduced to 3.8 once adjustment was made for
socio-economic factors. That is, a man with schizophrenia was four to
five times as likely to commit a violent act as a man in the general
population. For women, the equivalent pooled OR was 8.2 but there was a
much greater variation between the ORs in the individual studies than in
the studies that involved men.
"
"
Importantly the authors found that risk estimates of violence in people
with substance abuse but no psychosis were similar to those in people
with substance abuse and psychosis and higher than those in people with
psychosis alone. Finally, although people with schizophrenia were nearly
20 times more likely to have committed murder than people in the general
population, only one in 300 people with schizophrenia had killed
someone, a similar risk to that seen in people with substance abuse.
"
"
What Do These Findings Mean?
These findings indicate that schizophrenia and other psychoses are
associated with violence but that the association is strongest in people
with substance abuse and most of the excess risk of violence associated
with schizophrenia and other psychoses is mediated by substance abuse.
However, the increased risk in patients with comorbidity was similar to
that in substance abuse without psychosis. A potential implication of
this finding is that violence reduction strategies that focus on
preventing substance abuse among both the general population and among
people with psychoses might be more successful than strategies that
solely target people with mental illnesses. However, the quality of the
individual studies included in this meta-analysis limits the strength of
its conclusions and more research into the association between
schizophrenia, substance abuse, and violence would assist in clarifying
how and if strategies for violence reduction are changed.
"
From two other recent high quality papers used in the NICE schizophrenia
annual evidence update 2010
(http://www.library.nhs.uk/MENTALHEALTH/ViewResource.aspx?resID=344920&pgID=1
<http://www.library.nhs.uk/MENTALHEALTH/ViewResource.aspx?resID=344920&pgID=1>).
I can only read the abstract of these two papers which is a shame.
Large M, Smith G, Nielssen O. The relationship between the rate of
homicide by those with schizophrenia and the overall homicide rate: a
systematic review and meta-analysis. Schizophrenia Research 2009; 112(1-3).
http://www.ncbi.nlm.nih.gov/pubmed/19457644
"
BACKGROUND: It is widely believed that the rate of homicide by the
mentally ill is fixed, differs little between regions and is unrelated
to the total homicide rate. METHODS: We conducted a systematic review
and meta-analysis of population-based studies conducted in developed
countries of homicide committed by persons diagnosed with schizophrenia.
FINDINGS: We found that rates of homicide by people diagnosed with
schizophrenia were strongly correlated with total homicide rates
(R=0.868, two tailed, P<0.001). Using meta-analysis, a pooled proportion
of 6.48% of all homicide offenders had a diagnosis of schizophrenia (95%
confidence intervals [CI]=5.56%-7.54%). Rates of other homicides did not
contribute to the heterogeneity in the proportion of homicides committed
by those with schizophrenia (slope=-0.055, P=0.662). CONCLUSIONS:
Homicide rates by people with schizophrenia are associated with rates of
all homicides. It is therefore likely that both types of homicide have
some common etiological factors. Accordingly, measures to reduce the
likelihood of a person committing homicide during a psychotic illness
should not only attempt to optimise treatment, but include attention to
those factors associated with an increased risk of all homicides, such
as improving the social circumstances of disadvantaged patients,
treating substance abuse and reducing access to weapons.
"
The pooled proportion of 6.48% is high. Its also linked to the overall
homicide rate in different countries. The authors say "therefore likely
that both types of homicide have some common etiological factors" and
I'd like to read the paper to see how they explored this.
Richard-Devantoy S, Olie JP, Gourevitch R. Risk of homicide and major
mental disorders: A critical review. Encephale 2009; 35(6).
http://www.ncbi.nlm.nih.gov/pubmed/20004282
It doesn't paint a pretty picture. From the above study's abstract.
"Mental disorder increases the risk of homicidal violence by two-fold in
men and six-fold in women. Schizophrenia increases the risk of violence
by six to 10-fold in men and eight to 10-fold in women."
On the plus side for some and bad news for others.
"According to studies, we estimated that this increase in risk could be
associated with a paranoid form of schizophrenia and coexisting
substance abuse. The prevalence of schizophrenia in the homicide
offenders is around 6%. Despite this, the prevalence of personality
disorder or of alcohol abuse/dependence is higher: 10% to 38%
respectively. The disorders with the most substantially higher odds
ratios were alcohol abuse/dependence and antisocial personality
disorder. Antisocial personality disorder increases the risk over
10-fold in men and over 50-fold in women. Affective disorders, anxiety
disorders, dysthymia and mental retardation do not elevate the risk.
Hence, according to the DMS-IV, 30 to 70% of murderers have a mental
disorder of grade I or a personality disorder of grade II."
The result that the homicide rate for schizophrenia is also associated
with local homicide rate is interesting perhaps. None of that gets away
from the small increase in chance of being killed by someone with this
diagnosis. The risk is very small and far greater than the public
perception which is /every/ schizophrenic has the potential to kill. In
fact the greatest risk is the risk to life through suicide and I would
guess that people with this diagnosis account for a high proportion of
the 5706 suicides in .2008 in the UK.
None of that makes it any easier for a person with a diagnosis of
schizophrenia. These are comparisons of risk and though homicide is a
terrible thing it rarely happens so the reality of the risk is very low.
It is also not a predictor - a diagnosis of schizophrenia does not make
a person homicidal (or at least most people). The homicide and gender
statistics show men commit the vast majority of murders in the UK so
there is more risk from being male than from a schizophrenic. Neither of
those is a risk though. The probability of a person being killed by
another person in their lifetime is very low. It is mathematically true
to say that the risk is higher for being killed by a person with a
diagnosis of schizophrenia. That's undeniable. However were research to
be done on other labels that say nothing about the individual and who
they really are, for example "Black" or "Black male" or "male" or
"drunk" or "addict" or "psycho" or "axe-wielding" those could be shown
to be more risky than people with a diagnosis of schizophrenia. In all
those cases it applies that it is not a useful predictor of a person's
behaviour and the rational expectation would be to feel safe around a
Black, male, drunk, addicted, psycho schizo with an axe. Yes. I think
this extends to feeling safe around people with axes, in general (oh the
academic caveat emptor! lol).
A piece of information that can counter some of the science is the
studies showing the estimated lifetime prevalence of psychotic
conditions to be in the order of 10% however I've not read that study
and from other studies (I also haven't read) covered in another post the
stigma is attached to the word "schizophrenia" is much higher than the
word "psychosis" and the studies are done on people with a diagnosis of
schizophrenia but not other psychotic disorders or sub-clinical
syndromes like schizotypy (though this may soon become a normal state
that is an illness through DSM-V). I am unsure if there is a
differentiation between psychosis and schizophrenia. I think psychosis
is a state of consciousness that is also part of schizophrenia but may
be lumped together in the lay perspective.
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