Improvements in psychiatric treatments have
been cited as a likely reason for the decline in homicide rates due
to mental disorder in the last 30 years.
In a study
published in the August issue of the British Journal of
Psychiatry, researchers re-examined the official homicide
statistics from England and Wales between 1946 and 2004.
Analysis revealed that the rate of total
homicide and the rate of homicide due to mental disorder rose
steadily until the mid-1970s.
The data showed that the annual number of
homicides due to mental disorder rose from under 50 in 1957, to
well above 100 by the 1970s. The highest annual rate of 0.235 per
100,000 population was in 1973 and the absolute number peaked in
1979. Between 1957 and 1980, homicides due to mental disorder and
total homicides were strongly correlated.
However, in the subsequent 24 years
(1981-2004), homicides due to mental disorder declined and were
negatively correlated with the rate of homicide by people without
mental disorder. In other words, there was a reversal in the rate
of homicides attributed to mental disorder, which declined to
historically low levels, while other homicides continued to
rise.
The absolute number of homicides due to mental
disorder fell to levels not seen since the early 1950s, and the
rate has been at historic lows of 0.07 per 100,000 population or
lower since 2000.
The authors observed that the reasons for the
rise and fall in homicides attributed to mental disorder are not
clear cut. One possible explanation may have been changes in the
threshold for the finding of a verdict of diminished
responsibility, the largest group of such homicides. However, there
have been no changes to the official definitions of the defences to
murder since the reforms of the mid-1950s.
Another possibility is that methods of
detecting mental disorder before trial have changed over the past
50 years. But, if anything, the detection of mental illness among
prisoners is more likely to have improved over this time and it
seems unlikely that there has been a decline in the ability of
courts to detect the role of mental disorder.
Instead, the researchers propose that the
decline in homicide rate attributed to mental disorder is due to
improvements in treatment and in service organisation. The
introduction and increasing use of antipsychotic medication, the
greater awareness of the treatment of psychosis by primary care
providers after deinstitutionalisation, and the creation of
regional health authorities with responsibility for defined
populations, may have all contributed to the observed decline in
homicide since the 1970s.
This reasoning is also consistent with the
findings of recent studies in the UK and Australia, which suggest
that initial treatment of psychosis may reduce the risk of
homicide.