The number of homicides by mentally ill people is at its lowest ever level for more than fifty years, according to new research.
Figures from 2004 show there were less than 20 killings per year in England and Wales by people with a mental illness, a study in the British Journal of Psychiatry reported.
This is the lowest ever level since the 1950s, and is largely due to improved treatment, including medication, say the study’s researchers.
The study’s findings are likely to call into question how best to assess the number of killings attributable to mental ill health.
The government-backed National Confidential Inquiry into Suicide and Homicide by People with Mental Illness reported that in 2004 there were 64 homicides by people who had had contact with psychiatric services within 12 months of the offence.
It states there are a steady 50 homicides per year by people with a “history of mental illness”
But this month’s British Journal of Psychiatry (BJP) study stated homicides by people with a mental illness has been in a steep decline since 1970 when it peaked 120 homicides per year, to around 30 in 2000 and 20 in 2004.
Academics acknowledge that the “discrepancies” between the BJP study and the national inquiry figures are largely due to how homicides by people with a mental illness are recorded.
The BJP results were based mainly on court verdicts of “diminished responsibility” to indicate whether a killer had a mental illness. The national inquiry statistics are based on people who had previous “contact” with psychiatric services.
But psychiatrist Matthew Large, lead author of the BJP study, believes its figures are advantageous in that it recorded whether a homicide was committed because of mental illness, and not other factors.
“The advantage of the legal definitions used in [our] study is that the court has considered, usually with care and expert advice whether mental illness was a causal factor in the homicide,” Dr Large told psychminded.co.uk
“Mentally ill people may be more likely to commit a homicide for reasons other than mental illness. For example, patients with severe mental illness often drift to less economically favorable conditions where violence is more common.”
Dr Nicola Swinson, a clinical research fellow for the national inquiry and also a researcher in the BJP study, said the “discrepancies” between the studies were due to how the presence of mental illness was measured.
“As regards the most reliable way of measuring rates of mental illness, it really depends on what you’re interested in,” she said.
“At the inquiry…what we focus on is those in contact with services, as this would seem to be the most appropriate way of looking at potential changes to practice and policy within mental health services, and therefore at improving clinical care and reducing risk.”
Some critics say “sensationalist” media reports of killings by people with a mental illness led to the new “draconian” mental health act which comes into force in three months.
The new law allows the use of community treatment orders which aim to ensure that certain community patients diagnosed with a mental illness take their medication, and so are less likely to commit violence.
Mind’s policy officer Alison Cobb blamed media coverage for misconceptions about violence and mental illness.
“The number of homicides committed by people with mental distress have long been a tiny fraction of the total,” she said.
“But due to sensational media coverage of one-off cases, there has been a widespread misconception that they are more common than they really are.”