"We now have tools for developing neurobiological tests to detect patients at high risk for suicide," concludes Dr. J. John Mann, whose study into a possible predisposition for suicide appears in the current issue of the journal Nature Medicine.

Over 30,000 Americans intentionally kill themselves each year, and 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% 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."

Mann reviewed existing scientific literature to determine if neurotransmitters, chemical messengers in the brain, 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 to the brains of people who die from other causes.

Mann believes that 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," according to the report.

Neurologists and psychiatrists have already 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).

Mann points out that "lower CSF 5-HIAA has been found in schizophrenics with a history of suicidal behavior, compared to schizophrenics without such a history." Similar results have also been found in studies of patients suffering from personality disorders.

Mann notes that low serotonin levels may encourage all types of violent acts. So it is not surprising, he says, that relatively low CSF 5-HIAA levels have also been discovered in the cerebrospinal fluid of murderers and arsonists.

He believes that low serotonin activity may be linked to both genetics and developmental traumas, such as child abuse.

Mann believes CSF 5-HIAA testing could someday become a routine means of spotting those patients most vulnerable to suicide.

He also says that the 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," writes Mann.

SOURCE: Nature Medicine,

      Link Between Serotonin and Suicide Found with New Brain Imaging

      Centre for Addiciton and Mental Health, Toronto, Ontario Press Release

      Embargo: January 1, 2003 (Toronto): Not all people with

      clinical depression have low serotonin levels according to a

      study published in the January issue of The American Journal

      of Psychiatry.

      "There is a common misunderstanding that serotonin is low

      during clinical depression. It mostly comes from the fact that

      many antidepressants raise serotonin. This is a bit like saying

      that pneumonia is an illness of low antibiotics because we treat

      pneumonia with antibiotics," says Dr. Jeffrey Meyer, the

      principle investigator of the study, conducted by researchers at

      the Centre for Addiction and Mental Health (CAMH) and the

      University of Toronto.

      According to Dr. Meyer, the main reason people thought

      serotonin was abnormally low during depression is that suicide

      victims have more serotonin binding sites, which demonstrates

      lowered serotonin levels. However, not all people who are

      victims of suicide have clinical depression (probably about half

      do) and there are other psychiatric illnesses that increase the

      risk for suicide.

      The researchers used a brain imaging technique called positron

      emission tomography to scan people's brains for serotonin

      binding sites during episodes of clinical depression. What they

      found was that the serotonin abnormality happened in brains of

      people who had clinical depression and severely negativistic

      thinking. The study found that low serotonin levels can increase

      negativistic thinking. This is important because severely

      negativistic thinking is a major risk factor for suicide.

      Dr. Meyer says that this is an important finding in that some

      family members of people who commit suicide blame

      themselves. "It's important for people to understand that often

      the severely negativistic perspective of their loved ones in the

      midst of a clinical depression can be caused by chemicals in the

      brain," he says.

      Dr. Meyer is very positive about the future of treatment for

      depression with the aid of the brain imaging technique, "In the

      past, we could not look at brain chemicals in people - the brain

      was like a black box. With this new imaging technology, we

      can figure out how abnormal brain chemicals cause symptoms.

      If we can understand a mechanism for each symptom, we

      should be able to better understand the illness."

      So what are antidepressants that raise brain serotonin doing?

      Dr. Meyer suggests that replacing low brain serotonin is only a

      part of what antidepressants do. Other researchers have shown

      that raising brain serotonin gives brain cells instructions to

      grow, thrive and survive. Our understanding of clinical

      depression is getting more complicated, but this will lead to

      new advances in treatment.

      The Centre for Addiction and Mental Health (CAMH) is a Pan

      American Health Organization and World Health Organization

      Collaborating Centre and a teaching hospital fully affiliated with

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