Vol. 6, No. 4, 2000 Page 1&2

Low serotonin, aggression once again linked

Low levels of the neurotransmitter serotonin are strongly linked to impulsive, violent suicidal behavior, but a new study adds to evidence linking reduced serotonin levels to aggression even in the absence of suicidal tendencies.

Barbara Stanley et al. measured cerebrospinal fluid levels of the serotonin metabolite 5-hydroxyindoleacetic acid (5-HIAA) in 64 psychiatric patients with a range of disorders including bipolar disorder, major depressive or dysthymic disorder, schizophrenia, and schizoaffective disorder. None had a history of suicidal behavior. T The subjects were divided into two groups, based on high or low scores on measures of adult aggression.

"When mean CSF 5-HIAA levels of the two groups were compared," Stanley et al. say, "the aggressive group was found to have significantly lower CSF 5-HIAA concentrations than the non-aggressive group." This finding was true for all diagnostic categories. They note that aggressive subjects with low 5-HIAA levels were also more impulsive than non-aggressive subjects, which is consistent with evidence l linking reduced serotonin levels and impulsive behavior.

The researchers conclude, "There is an association between aggressive behavior and serotonergic dysfunction independent of suicidal behavior in patients with [psychiatric] disorders who exhibit relatively milder forms of aggressive behavior." They say this supports and extends previous studies linking low CSF 5-HIAA levels to aggression in impulsive murderers, arsonists, and individuals convicted of infanticide, as well as research showing that recidivists have lower leve els of the serotonin metabolite than non-recidivists. They also point to research showing a relationship between low serotonin activity and aggression in dogs, saying, "Since animals may be presumed to be free from major psychiatric disorders, anim mal studies demonstrate the generalizability of the relationship between lower serotonin activity and impulsive aggression, and support our conclusion that the relationship is independent of suicidal behavior."

The researchers say the association between aggression and suicidal acts may indicate that the two behaviors "have a common behavioral denominator, such as impulsiveness, which is associated with a common biological correlate." They also say their finding gs suggest that impulsive aggression could be reduced by drugs targeting the serotonergic system.


"Association of aggressive behavior with altered serotonergic function in patients who are not suicidal," Barbara Stanley, Avraham Molcho, Michael Stanley, Ronald Winchel, Marc J. Gameroff, Bruce Parsons, and J. John Mann, American Journal of Psychiatry, Vol. 157, April 2000, pp. 609-614. Address: Barbara Stanley, Unit 42, New York State Psychiatric Institute, 1051 Riverside Drive, New York, NY 10032.

Related Article: [2000, Vol. 6]

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