Despite some highly publicised incidents in recent years, people with schizophrenia rarely commit random homicide, research shows.
Pooling data from seven studies in four countries, researchers found that the odds of a person with schizophrenia killing a stranger were one in 14 million people per year.
The risk appears even lower if the disorder is being treated with antipsychotic medication, the investigators report in the Schizophrenia Bulletin.
When they looked at 42 incidents in which someone with schizophrenia killed a stranger, they found that nearly two-thirds of those offenders had never been treated with medication.
They conclude that it is "exceptionally rare" for someone with schizophrenia to kill a stranger -- and that earlier and continued treatment of the disorder could make these events rarer still.
Most schizophrenics violent
Schizophrenia is a brain disorder that causes people to break from reality, with symptoms such as hallucinations, paranoia and unusual thoughts and perceptions.
Most people with schizophrenia are not violent, but studies show that they are more likely than people without the disorder to commit violent crimes. This is especially true if a person with schizophrenia abuses drugs or alcohol, or had a history of violence before developing the brain disorder.
People with schizophrenia are responsible for a disproportionate number of homicides; while they account for about 0.5% of the world's population, they are estimated to commit 6.5% of homicides worldwide, according to Dr Olav Nielssen of the University of Sydney in Australia, the lead researcher on the new study.
Most of the victims, though, are family members, Nielssen said, and in nearly half of these cases, the person's schizophrenia had never been treated.
The findings are based on seven studies from Europe and Australia looking at homicides by people with schizophrenia. The estimated annual rate of "stranger homicides" ranged anywhere from 1 in 7 million to 1 in 18 million people per year.
How the study was done
The researchers also compared 42 cases of stranger homicide with 42 in which the victim was a family member. They found that the former were more likely to be committed by a schizophrenic individual who was homeless, or had a history of severe childhood or adult behavioural problems, including violence.
In both groups, more than half of the offenders had never been admitted to a psychiatric hospital or placed on antipsychotic medication. Of the 42 who killed a stranger, 64% had never received drug treatment.
Some highly publicised homicides in Canada, the US and the UK in recent years have led to law changes designed to compel people seen by mental health services to take any prescribed antipsychotic medications.
However, Nielssen said, "Because a large proportion of both stranger and family homicides occur prior to initial treatment, laws designed to ensure continued treatment of known patients will not have much effect in preventing homicides."
Instead, he asserted, a more effective approach would be to get people treated sooner, when their initial psychotic symptoms arise. In wealthier countries, Nielssen noted, the lag time between first symptoms and initial treatment is one year, on average.
He and his colleagues argue that a key obstacle to early treatment is so-called "dangerousness" laws, which require that a person be deemed a danger to himself or others before involuntary treatment is an option. Such laws are in place in most US and Australian states, half of Canadian provinces and in several European countries, Nielssen noted.
He said that instead of focusing on a patient's potential danger, mental health laws should be based on the individual's need for treatment and competency to refuse it. – (Reuters Health, October 2009)