Empiricists
study the world as it is. Reformers try to create the world
as it should be. These Accountants and Missionaries do not always see eye to
eye.
The
history of the treatment of the mentally ill makes painful reading,
at least to modern sensibilities. The mentally ill have been abused, ridiculed,
stripped of dignity and legal rights, and shunned by the public, who feared
their madness. The mad were seen as dangerous and a nuisance. In their madness
they might strike out at you, subject you to abuse, to unpleasant sights and
embarrassing outbursts, and at the very least would need help and compassion
while not being able to give much in return. For example, when we are depressed
we have less to offer our friends, and more need of their support,
encouragement and tolerance for our lack of contribution.
In the face of these historical abuses, in 1796 the
Quakers’ York Retreat offered humane
and moral treatment, on the Christian assumption that, whatever the sufferer’s behavioural
degradation; the inner light of humanity could never be extinguished. Since
that time we have become kinder, and more liberal and generous about disordered
comportment. We know that not all mental illness is terminal, irreversible and
dangerous. Nowadays we want to reduce stigma, that badge of shame and disgrace which some
in society attach to those with characteristics, behaviours or beliefs they
find disturbing. Hence a missionary movement among mental healthcare
professionals to normalise mental distress, to understand the perspective of
even the oddest point of view, and to break down the shame of admitting a mental
affliction.
I was always somewhat surprised when, even in the
privacy of my office, beset with problems and worries, my patient’s first words
after bursting into tears were always “I’m sorry”. I would mumble something
about not needing to apologise for having emotions, but in the purely social
sense, my tearful patients were right. They had sent out a very powerful
distress signal, generally without meaning to, had broken the taboo of
emotional restraint and now had to justify this dramatic call for assistance.
They felt they were being a drag, and didn’t want to be.
So, if every right thinking person in the psycho-business
should be de-stigmatising mental illness, how
do we deal with the fact that some of the mentally ill are dangerous? Ideally,
we would follow the empirical tradition, and give an accurate and balanced message:
“Most people with mental illness are no more dangerous than anyone else, but a
minority are more prone to violence. It is difficult to predict dangerousness. Here
are the facts and you can judge for yourself”.
What are the facts? In the behavioural sciences, facts are always a work in progress,
but the overall picture is now reasonably clear: schizophrenics are more violent
as a category, something of the order of 4 times more violent, perhaps even 5
times higher. Given that most people are not very violent at all, being four
times more violent is still not very dangerous, but it is an appreciable
increase. Drug takers are 10 times more violent. Perhaps shunning some people
is a prudent policy. It is certainly within the discretion of any citizen to
judge that a fourfold increase in even a very small risk is something worth
avoiding, particularly if it can be done without too much bother.
At this point we need to cover just a few technical
issues. The best technique to determine violence rates is a prospective study
in which you define a population sample and study them long term. Birth cohorts
are the gold standard. Follow this large sample, find out who gets
schizophrenia, and then take objective measures of violence (arrests, cautions,
convictions, jail sentences for example) and then you have your rates of
violence, both absolute and relative to those who do not have schizophrenia. Here are some findings, which I have drawn from a
paper I will discuss later on:
Hodgins (1992), in a 30-year follow-up of an unselected Swedish birth
cohort, found that compared with those with no mental disorder, males with
major mental disorder had a 4-fold and women a 27.5-fold increased risk of
violent offences. No separate data were provided for schizophrenia. A later
study using the same methodology revealed similar findings (Hodgins et al, 1996).
The first cohort study to demonstrate the
quantitative risk of violent behaviour for specific psychotic categories
followed an unselected birth cohort of 12 058 individuals prospectively for 26
years (Tiihonen et al, 1997). The risk of violent offences among males with
schizophrenia was 7-fold higher than controls without mental disorder.
Arseneault et al (2000) studied the past-year prevalence of violence in 961 young
adults who constituted 94% of a total city birth cohort. Three Axis I disorders
were uniquely associated with violence after controlling for demographic risk
factors and all other comorbid disorders: alcohol dependence, marijuana
dependence and schizophrenic spectrum disorder.
Probably the most important study in the violence
literature to date is that of Swanson et al (1990). Using a sample of 10 059 adult residents from
Epidemiologic Catchment Area (ECA) study sites (Eaton & Kessler, 1985), the authors examined the relationship
between violence and psychiatric disorder. Eight per cent of those with
schizophrenia alone were violent, compared with 2% of those without mental
illness. Comorbidity with substance abuse increased this percentage to 30%.
Two factors appear to discriminate those with
schizophrenia at increased risk of committing violent acts: comorbid substance
abuse and acute psychotic symptoms.
It is important to note that because there is
an increase in violence risk in those without comorbidity, substance abuse
merely increases the level of risk rather than causing it (Arsenault et
al,
2000; Brennan et al, 2000). Hence, the risk from substance abuse appears to be
additive.
In Dunedin, New Zealand, 94% of a total city
birth cohort were followed up at age 21 years. Without considering comorbidity,
just over 10% of past-year violence committed by these young adults was
attributable to schizophrenic spectrum disorders
So, how has psychiatry responded to this awkward junction of facts and
missions? The Royal College of Psychiatrists currently gives the following
statement as a key fact about schizophrenia: Many people think that schizophrenia makes people
violent. This is the exception, not the rule. People with schizophrenia are
more likely to be victims of violence by others.
Comment: Well, this presentation
is not entirely balanced. Gang members are also likely to be victims of
violence by others. They are also violent themselves. Schizophrenia makes
people four times more violent. Their violence is an exception, but these
exceptions happen four times more frequently.
So, what other exhibits
should we look at?
One of the better
known papers in the field is Walsh, Buchanan, and Fahy
(2002) Violence and schizophrenia: examining the evidence,
from which I had drawn the above papers on violence rates.
They say: It is now accepted
that people with schizophrenia are significantly more likely to be violent than
other members of the general population. A less acknowledged fact is that the
proportion of societal violence attributable to schizophrenia is small.
Comment: So, they are more violent,
but make a small contribution to “societal” violence? How can that be so? Now
you see it, now you don’t? Or is there some real reason why their increased
violence does not have an impact on society?
Here is their argument, in the
expanded form of a subsequent book chapter: Criminal and
violent behaviour in schizophrenia by Walsh and Buchanan in (Eds) Murray,
Jones, Susser, van Os and Cannon (2003) The
Epidemiology of Schizophrenia, Cambridge University Press.
It
is now generally accepted that people with schizophrenia, albeit by virtue of
the activity of a small subgroup, are significantly
more likely to be violent than members of the general
population,
but the proportion of societal violence attributable to this group is small.
They continue thus:
To
prevent unnecessary stigmatization of the seriously mentally ill, with all the attendant
difficulties, it is the duty of researchers to present a
balanced picture. By neglecting to report measures of both relative and
absolute risk a skewed picture may emerge. An example of a balanced report found
that men with schizophrenia were up to five
times more likely to be convicted of serious violence than the general population
(Wallace et al., 1998). Results also presented indicated that 99.97% of those
with schizophrenia would not be convicted of serious violence in a given year and
that the probability that any given patient with schizophrenia will commit homicide
is tiny (approximate annual risk 1:3000 for men and 1:33000 for women).
Comment: Although intending to be balanced, this is
another misleading presentation. Fahy did better in earlier papers in which he
said that schizophrenics were about 4 times more violent than ordinary members
of the public, but that the absolute rates were very low. Let us study some of
the assertions:
“99.97%
of those with schizophrenia would not be convicted of serious violence in a
given year”.
Comment: Presumably this is intended to be
reassuring. What does 99.97% mean? It sounds like 100%. In his marvellous “Reckoning with Risk” (2003)
Gerd Gigerenzer showed that percentages with decimal points were almost
impossible for most people to understand. (I had to count the zeros, and got it
wrong the first time round). The best way to make the numbers transparent is to
convert them to natural frequencies, ordinary numbers without fractions or
decimal points. Using this approach we can say that 9997 schizophrenics in
10,000 won’t be convicted of violence, but 3 will. So 3 in10,000 schizophrenics
(10,000 minus 9997 = 3) will get convicted of serious violence. Using the usual
yardstick for rare events, that means that 30 per 100,000 schizophrenics are
convicted of serious violence each year.
What is the rate of convictions per thousand in the
general public? It has not been given for comparative purposes, so the
percentage figure is difficult to assess. However, it has been admitted that
schizophrenics are 5 times more violent. Thus we can calculate that the rate
for mentally well citizens would be roughly 6 per 100,000. One popular proposal
to make statistics easier to understand is to place the frequency statistics in
the context of villages, towns and cities. Therefore, if you spent a year in a
town of 100,000 schizophrenics you might not be at too much risk yourself, but
there would be about 30 violent crimes in that town. You might find this
somewhat alarming. A neighbouring town of ordinary citizens would have 6
violent crimes to contend with. People will be people, you may say, but from a
civilized point of view, every violent crime is unnecessary. It is likely that
the reputations of these towns would differ significantly. Which town would you
wish to live in, if you were free to choose?
(Paradoxically, the Press in the first town would
never bother to report that the accused was a schizophrenic. It would be
redundant, so in that town the media could not be accused of stigmatising
mental illness.)
The other issue, never covered in these discussions,
is that the overall risk rate is not a good predictor of the perceived personal
risk rate. Violence is most likely to come from someone you know, with whom you
are in a dispute, for whatever reason, usually because of tangled love affairs,
business deals and, most of all, criminal activities. Most people know this,
and know the sort of people they ought to avoid. The fear caused by
schizophrenia is that it is associated with totally motiveless crimes. There is
no way you can protect yourself by regulating your behaviour or your friendship
patterns. You might be sitting on a bus, minding your own business, when a
passing stranger stabs you to death in a matter of fact way, as happened
recently to a school girl. It may seem odd to a statistician, but that sort of
thing bothers us. In Kahneman and Tversky’s phrase, it has “salience”. To die at the hand of a
jilted lover is bad enough, but to die because of a delusion is senseless, and gives
us no chance of security. We fear more than statistics.
Now we go on to the murder statistics: The probability that a schizophrenic will
commit murder each year is 1 in 3000.
Comment: Why so high? Can that be right? (I have
checked the publication to make sure).That translates to a murder rate of 33
per 100,000. In Britain the annual murder rate is 1.2 to 1.4 per 100,000. Out
of charity I will take the higher estimate of 1.4. (The more peaceable a
society, the more it makes sense to give the figures per million, and 14 per
million is the usual British estimate). This suggests that schizophrenics are
23 times more murderous. Something wrong here, I fear. Are these authors really
arguing that 1:3000 is a low rate? It would be like moving from the UK to South
Africa or Columbia, currently among the most murderous nations on the planet. I
hope there is something wrong with their figures, because if they are accurate
the implications are alarming. There must have been a miscalculation, because
if the figures above are correct in showing that there are 30 violent crimes
per 100,000 schizophrenics, then fewer of them will go on the whole way to
murder, and the homicide figures should be much lower.
A few years ago the President of the Royal College of Psychiatrists was reported as
having said that schizophrenics caused only about 10% of the violence. Given
that schizophrenics are at most 1% of the population (and probably only 0.7%)
this was tantamount to saying they were at least 10 times more dangerous than
normal. Four or five times are the more accurate figures.
Looking at the more recent Royal College of
Psychiatry report: Rethinking risk to others in mental health services Final report of a scoping group (June 2008) provides us with fresh estimates of
dangerousness.
It
is estimated that 5% of homicides are committed by people with a diagnosis of
schizophrenia. (page
18)
Comment: A truthful statement. That
is exactly what one would expect, if schizophrenics were 1% of the public and
committed 5 times more violent crimes. Their greater rate of violence
translates directly into a proportionately greater share of “societal”
violence.
The
incidence of mental illness among those remanded for acts of violence is
relatively high: Taylor & Gunn (1984) found psychosis in 11% of those
remanded for homicide and 9% of those remanded for other acts of violence.
Similarly, violence in mental health services is not infrequent. The UK700
study (Walsh et al, 2001) found
physical assaults had been committed by 20% of patients over a 2-year period
and 60% had behaved violently over the same period. Taking the figure of 1
homicide per 20 000 patients with schizophrenia per annum, over the 20 years of
a typical patient ‘lifetime’ (assuming active disease from the age of 20 to 40
years) the risk per patient is 1 in 1000 (Maden, 2007). The occurrence of a
homicide by a patient with a mental disorder also has potentially devastating
implications for the professionals involved. (page 20).
Comment: The homicide would have devastating implications for the victim
and the victims’ family and friends. It would have serious implications for the professionals, whose careers can be
damaged, but they would not face capital punishment. Having had friends in this
category, I can testify that it is an awful process for them, but most of their
colleagues know it could happen to any of them doing front line psychiatric
work: “There but for the grace of God go
I”.
The next point that this report
gives the homicide risk as 1 per 20,000 patients per annum, not the 1 in 3000 each
year given by Walsh and Buchanan. Taking these new figures, they suggest that
the lifetime risk of homicide over 20 years is: the addition of 1 in 20,000
risks per annum for 20 years of active exposure, namely 20 in 20,000, or 1 in
1000. In comparison, the risk of being murdered by an ordinary member of the
public is 1.4 per 100,000. Over 20 years that comes to 28 per 100,000 or 1 per
3,571. Thus, these figures suggest schizophrenics are 3.5 times more violent,
which is within the published range. These figures look reasonable.
So, can we detect and prevent
violent events?
For
example, it has been calculated – using the average of all the tests assessed
by Buchanan & Leese (2001) – that if 5% of the patient population were within
a high-risk category, use of the tests would correctly identify 8 people out of
every 100 in the group who would go on to commit acts of violence but
misidentify as violent the other 92. In fact, fewer than 1% of community
patients will commit serious violence over a period of a year, which means that
the tests would correctly identify only 3 patients out of 100. Homicides occur at a rate of 1 in 10 000
patients suffering from a psychosis, per annum, which makes prediction
impossible (Shergill & Szmukler, 1998; Dolan & Doyle, 2000). (page 23)
Comment:
Two problems here. First, this is significantly different risk estimate: in
that on page 20 it was 1 homicide per 20 000 patients
with schizophrenia per annum and on page 23 it is 1 in 10 000
patients suffering from a psychosis, per annum. This is confusing, but presumably
it refers to the symptom of psychosis, rather than the diagnosis of schizophrenia,
and other conditions can induce psychotic behaviour, so we should probably put this
estimate aside for the moment, though it is twice as high as the former figure.
Second,
low base rates do not necessarily make prediction impossible, but simply very
difficult in the absence of valid indicators. Phenylketonuria occurs in 1 in 10,000 to 15,000
newborns (higher in the US) and most cases are detected by screening. Tandem
mass spectrometry is claimed to be 100% sensitive and 98% specific, which means
that virtually all cases are picked up and the test rarely misclassifies other
conditions as being phenylketonuria.
Treatment is
started promptly, and as a result, the severe signs and symptoms of the classic
condition are rarely seen.
Have pity on Psychiatry.
As the quotation above reveals, current tests do have the sensitivity and
specificity requires to usefully predict violence, let alone murder. The best test that forensic professionals
have is a detailed interview leading to a risk assessment, though there is
still debate about precisely what this risk assessment should contain. There
must also be checking of records, and good links with social services and the
Police. Often, this still defeats the current organisation of services.
Resource constraints make the problem more difficulty. Poorly trained or poorly
motivated ward staff sometimes do not follow risk protocols, even when they are
written in to the patient notes.
Note that this
unsatisfactory state of affairs does not have to continue for ever. One good
indicator seems to be patients trying to re-admit themselves to hospital.
Failure to take medication, and over-indulgence in alcohol and drugs is another
indicator. It is very hard to detect the signal from among the noise, but we
have to keep trying. Perhaps if we could monitor electronically, as if the
person had diabetes, we could eventually predict with less error. What would we
monitor? Thoughts? Arguments? Drugs in the bloodstream?
So,
how can one argue that schizophrenia makes people more violent, but that this
does not cause much “societal violence”? This boils down to a particular
statistical technique, the calculation of population-attributable
risk per cent (PAR%): the percentage of violence in the population that can
be ascribed to schizophrenia and thus could be eliminated if schizophrenia was
eliminated from the population. Stand back from any calculations, and you
already know the answer. If 1% of the population has schizophrenia, and they
account for 5% of the violence, then curing them of the condition (or just the
violent aspects) would reduce societal violence by 5%. It is a matter of
perspective whether you think that this accounts for relatively little societal
violence. To me, this line of argument seems like trying to wish away a finding
by changing the currency of account. I think it is better for researchers to
publish their results on the risks of violence in schizophrenia, which is higher
in relative terms but low in absolute terms, without excursions into concepts
of “societal violence” as a false comparator. It is a bit like saying that
someone who drives a gas-guzzling Hummer has little societal impact because
they contribute only a very tiny fraction of the world’s pollution. Don’t move
from one metric to the other for rhetorical purposes.
So, to summarise
what psychiatrists are telling us about schizophrenia and the risks of
violence: there is general agreement that schizophrenic men are four to five
times more violent than the rest of the population, but the absolute rates of
all violence are mercifully low. The public should make up their own minds how
they wish to respond.
