Psychosis Rarely Begets Murder, Experts Say: Demographics Better Predict Violence Than Does Mental Illness-Except for Substance Abuse Disorder

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TORONTO -- Even movies and popular songs refer to the idea that there are dark and dangerous mentally ill persons who have the capacity to become "psycho killers."

The more appropriate term, however, might be "personality disorder killer," according to those leading a session at the annual meeting of the American Psychiatric Association.

The session was conducted by three forensic psychiatrists who said they were inspired by the idea that the general public has what may be an inordinate fear of psychotic individuals committing murder.

The newspaper is one place where the public gets its impressions of the mentally ill, and one survey of general media content found that 39% of newspaper stories with reference to mental illness focus on dangerousness and acts of violence, and that those stories get more prominent placement than do stories about treatment or other aspects of psychiatry, said Dr. Susan Hatters Friedman, who is with the department of psychiatry at Case Western Reserve University in Cleveland.

The National Institute of Mental Health-funded National Comorbidity Survey, conducted in 2005, found that those with depression and anxiety disorders were three times more likely to commit acts of violence, and those with bipolar disorder were eight times more likely, but the public impression that the mentally ill are more dangerous probably is exaggerated, she said.

The survey found that demographics were a more important predictor of violence than was a psychiatric condition, except for substance abuse disorder.

Several studies have investigated how frequently psychiatric patients murder or attempt murder, and it is not uncommon, Dr. Hatters Friedman said. One British study of 718 convicted murderers found that 34% had a history of a mental disorder.

In that study, however, only 10% of the murderers had symptoms of their disorder at the time of the killing, and most were not under any psychiatric care.

Moreover, contrary to the public's sense of dread, persons with mental disorders appear to be less likely to kill strangers, she said. The investigators in the British study reported that the individuals with a history of a mental disorder killed a stranger in only 7% of cases, versus 25% of the cases where the murderer had no psychiatric history.

The terms sociopath and psychopath are the ones the public might use to refer to someone who is mentally ill with homicidal tendencies, but those terms are not in the Diagnostic and Statistical Manual, said Dr. Joy Stankowski, also of Case Western Reserve.

However, when those terms have been defined, the definitions list traits that fall squarely within the characteristics of the cluster B personality disorders--antisocial, borderline, narcissistic, and histrionic. The sociopath lacks empathy and conscience. The psychopath is impulsive and persistent, and a violator of societal norms, she said. …