The study, by the National Confidential Inquiry into Suicide and Homicide by People with Mental Illness at The University of Manchester, also found that in-patient suicides have fallen to their lowest recorded figure and that patient suicides have fallen most sharply in people in their early 20s.

The researchers, led by Professor Louis Appleby, the government's Health and Criminal Justice Tsar, reported that the number of homicides committed by people who were suffering from schizophrenia or who were psychotic at the time of offence had fallen in 2005 and 2006 -- the most recent years for which figures are available.

Although the report's authors, based in the University's Centre for Suicide Prevention, say it is too early to conclude whether this fall was the start of a new downward trend, they concluded that a previously reported rise in homicides by mentally ill people had not continued.

"In our previous annual report, we reported that the number of people convicted of homicide who were psychotic at the time of the offence had shown an unexplained rise between 1997 and 2005," said Professor Appleby.

"In our latest report we have examined additional data for this period in an attempt to explain this rise in homicide, although we have also presented evidence that the increase has not continued."

The Inquiry team examined a number of factors that might explain the increase in homicide rates to 2005 by people -- both patients and non-patients -- with psychosis. These included:

• an increase in the rate of psychosis among immigrant populations
• an increase in homicide in urban populations where psychotic illness is more prevalent
• an increase in drug or alcohol misuse.

The report found that of these possible explanations, only the increase in drug and alcohol use could account for the rise.

"We examined reported history of drug and alcohol misuse of perpetrators and found there was a significant increase in the number of homicides by people with psychosis who also had a history of drug and, to a lesser extent, alcohol misuse," said Professor Appleby, citing cannabis, cocaine and crack cocaine, and amphetamines as the drugs most often used.

"On the basis of our data, the likeliest explanation for the rise in homicide by people with psychosis up to 2005 is the use of drugs or alcohol or both, although we were not able to demonstrate cause and effect. Our findings reinforce the need for mental health services to tackle the drug misuse that is common in young people with mental illness."

The Inquiry also examined homicides by mental-health patients -- defined as individuals who have had contact with mental-health services in the previous 12 months -- between 1997 and 2006 and found that, of the two to three homicides per year by in-patients, most were suffering from schizophrenia and the homicide occurred after leaving the ward without staff agreement.

The authors suggest that patient absconding could be reduced through better understanding of the factors on the ward that trigger patients to leave the ward without permission and through better ward design more generally.

Suicide rates among mental-health patients between 1997 and 2007 have fallen overall, particularly among in-patients (from 219 deaths in 1997 to 118 in 2007), but there are marked differences between age groups.

The number of suicide deaths among younger patients has fallen substantially and more than the drop in suicide rates for this age group in the general population. However, the report, funded by the National Patient Safety Agency, found that suicides among patients aged 45 to 64 are increasing in frequency.

Note: If no author is given, the source is cited instead.

• Today's Healthcare
• Mental Health Research

• Mental Health
• Psychiatry

• Public Health
• Bioethics

• Dopamine hypothesis of schizophrenia
• Suicide
• Pap smear
• Hallucination
• Psychosis
• Paranoia