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Free L-tryptophan plasma levels in antisocial violent offenders
J Tiihonen1, M Virkkunen, P Räsänen
1Department of Psychiatry, University of Helsinki, P.O. Box 320, 00029 Hus, Finland. jari.tiihonen@hus.fi
Rationale:
Several studies have shown that impulsive violent behavior is associated with reduced serotonin metabolism in the brain, but no data exist on possible alterations of the serotonin precursor (free L-tryptophan) levels among violent offenders.
Objectives:
To study free L-tryptophan and kynurenine plasma levels among antisocial violent offenders.
Methods:
Free L-tryptophan and competing amino acid (CAA) plasma levels were measured among 19 male impulsive antisocial violent offenders and 19 age-matched healthy male controls.
Results:
Mean free L-tryptophan/(CAA) plasma levels were 160% (95% CI 116%-204%) higher among offenders than controls (P=0.000). Seventeen of the 19 offenders (89.5%) had values of more than 2 SD above the mean value of controls. The levels of kynurenine, the major metabolite of tryptophan, were slightly increased in offenders.
Conclusion:
Free plasma L-tryptophan/CAA levels were markedly increased among antisocial violent offenders indicating a disturbed tryptophan metabolism.
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