The P&S Journal: Spring 1998, Vol.18, No.2
Serotonin: Marker of Suicide Risk
Low levels of the neurotransmitter serotonin in the brain may point to an increased risk for suicide. "We now have tools for developing neurobiological tests to detect patients at high risk for suicide," says Dr. J. John Mann, whose study into a possible predisposition for suicide appeared in the January 1998 issue of Nature Medicine.
More than 30,000 Americans intentionally kill themselves each year, and Dr. Mann says that despite enormous advances in psychiatric care, "there has been relatively little change in suicide rates over the last quarter of a century."
He also notes that while 90 percent of suicides are linked to pre-existing mental illness (most often depression, schizophrenia, and substance abuse), some patients seem more likely to attempt suicide than others, suggesting that they "have a vulnerability or predisposition to suicidal behavior."
Dr. Mann, P&S professor of psychiatry and director of neuroscience at the New York Psychiatric Institute, reviewed existing scientific literature to determine if neurotransmitters might play a part in this predisposition. He found that autopsies performed on the brains of suicide victims often reveal lower levels of serotonin activity in the brain region called the prefrontal cortex compared with brains of people who die from other causes.
Dr. Mann says serotonin acting in this area of the brain may help inhibit violent impulses. This means that reduced serotonin activity might "result in impaired inhibition and a greater propensity to act on powerful feelings such as suicidal or aggressive feelings."
Neurologists and psychiatrists have developed a means of gauging serotonin levels in living patients, by measuring levels of a breakdown product of serotonin called 5-HIAA in cerebrospinal fluid (CSF).
"Lower CSF 5-HIAA has been found in schizophrenics with a history of suicidal behavior," Dr. Mann says, "compared to schizophrenics without such a history." Similar results have been found in studies of patients suffering from personality disorders.
Dr. Mann notes that low serotonin levels may encourage all types of violent acts. Relatively low CSF 5-HIAA levels have been discovered in the cerebrospinal fluid of murderers and arsonists. Low serotonin activity may be linked to both genetics and developmental traumas, such as child abuse.
CSF 5-HIAA testing could someday become a routine means of spotting patients most vulnerable to suicide, Dr. Mann says. Newer antidepressant drugs, such as the serotonin reuptake inhibitors, have the potential to raise serotonin activity levels while reducing the danger of overdose. Use of these drugs has the potential for reducing suicide rates, Dr. Mann says.