Free L-tryptophan plasma levels in antisocial violent offenders

Rationale: Several studies have shown that impulsive violent behavior is as sociated with reduced serotonin metabolism in the brain, but no data exist on possible alterations of the serotonin precursor (free L-tryptophan) leve ls among violent offenders. Objectives: To study free L-tryptophan and kynu renine plasma levels among antisocial violent offenders. Methods: Free L-tr yptophan and competing amino acid (CAA) plasma levels were measured among 1 9 male impulsive antisocial violent offenders and 19 age-matched healthy ma le controls. Results: Mean free L-tryptophan/(CAA) plasma levels were 160% (95% CI 116%-204%) higher among offenders than controls (P=0.000). Seventee n of the 19 offenders (89.5%) had values of more than 2 SD above the mean v alue of controls. The levels of kynurenine, the major metabolite of tryptop han, were slightly increased in offenders. Conclusion: Free plasma L-trypto phan/CAA levels were markedly increased among antisocial violent offenders indicating a disturbed tryptophan metabolism.