Vol. 9, No. 1, 2003 Page 5
Murderers who commit additional crimes after their initial release show evidence of impaired dopamine system activity, according to a recent study.
Anna Maria Dåderman and Lars Lidberg measured levels of metabolites of the neurotransmitters serotonin, noradrenaline, and dopamine in 29 men convicted of murder and committed to a forensic psychiatric ward. Later, they conducted a follow-up study to determine which of the men committed additional crimes after being released. The men were followed for an average of 16 years after their original crimes.
Of the subjects, 14 committed additional crimes. Nine of these committed violent crimes, and one was convicted of another murder.
Unlike previous studies which found unusually low levels of the serotonin metabolite 5-HIAA in violent offenders who relapsed, Dåderman and Lidberg detected no significant reductions in 5-HIAA or the noradrenaline metabolite HMPG in repeat offenders. However, their data revealed a significant reduction in the dopamine metabolite HVA among recidivists.
This finding, the researchers say, "may be in line with the assumption that the level of dopamine is related to seeking potential reward or 'kicks.' Offenders who have a tendency to commit crimes characterized by danger and novelty seeking (such as robbery, weapons offenses and theft) may constitute such a group."
"Relapse in violent crime in relation to cerebrospinal fluid monoamine metabolites (5-HIAA, HVA and HMPG) in male forensic psychiatric patients convicted of murder: a 16-year follow-up," A. M. Dåderman and L. Lidberg, Acta Psychiatrica Scandinavica, Vol. 106, No. S412, June 2002, 71-4. Address: Anna Maria Dåderman, Department of Clinical Neuroscience, Occupational Therapy and Elderly Care Research, Division of Forensic Psychiatry, Karolinska Institute, Huddinge, Sweden.