Sufferers from mental illness who abuse drugs or alcohol are much more likely to be violent than those who do not, a conference on psychology and the law was told yesterday.
Research into the effects of alcohol and drug-abuse on those who suffer from an underlying mental illness was described by Prof John Monahan from the University of Virginia in the US. He told the international conference at Trinity College Dublin that the belief that those with mental disorders were likely to be violent had been around for a long time and had led to stigmatisation and discrimination against them.
In recent decades, there had been a shift towards "risk assessment" in public policy towards the mentally ill. However, many of the studies were limited or flawed, he said.
He described research he had led, which was sponsored by the MacArthur Foundation and was interdisciplinary. It took a sample of more than 1,000 people who had been in hospital because of some mental disorder.
Three sources were used in establishing whether they had been involved in a violent incident over a number or months - themselves, the person closest to them, and independent agencies such as the police. When all sources were taken together, 27 per cent were found to have been involved in a violent incident.
However, this was higher among those who were substance-abusers, which made up 20 per cent of the sample. Only 5.6 per cent of those who were not substance-abusers had a violent incident over a 10-week period, compared with 4.6 per cent of a sample of the general population in the area where they lived.
When this was examined more closely it was found that among the general population, substance-abusers were almost four times more likely to have a violent incident than non-abusers.
Among the patients the proportions were the same, but a much higher proportion of the patients abused substances. Therefore substance-abuse emerged as a strong risk factor.
Others were the seriousness of the mental disorder, whether the person had been abused as a child, the number of arrests they had had and whether they had committed a recent violent act.
The study also found that treatment made a significant difference. Nineteen per cent of those who received no treatment were violent in the 10 weeks following their release, while this was only 6 per cent among those who received treatment.
Ms Deborah Browne of UCC told a seminar at the conference that foster care could itself produce behavioural problems, leading to criminal behaviour.
She said foster care placements were most likely to fail where there were discipline problems, conflict with other children, self-destructive tendencies and problems of personal hygiene.
A high proportion of these problems followed abuse and neglect. Often the child's problems were not dealt with when they were brought into foster care.
Instead they flourished, a crisis developed, the child was moved, leading to a pattern of crisis placements and multiple care placements. This in turn led to further emotional and behavioural problems. She described two case studies which illustrated this.
In one a girl came into care at the age of four with problems arising from abuse. She received no counselling or psychotherapy, and the foster parents had no training to deal with the effects of the abuse. The foster care inevitably broke down and she ended up in a detention centre. At 16, she was involved in seriously anti-social behaviour.
The second example was of a girl who came into care as a baby, but after four years her foster mother could not keep her due to her own ill-health. She had eight foster placements in 10 years and behavioural problems developed.