Background. Aggression has been suggested to be
related to abnormal brain 5-HT activity. This amine is synthesized in
brain from tryptophan, which is transported through the
blood–brain barrier in competition with other amino acids. The
relationship between tryptophan and its endogenous amino acid
competitors in plasma might thus influence the availability of
tryptophan in the brain and consequently brain 5-HT activity.
Methods. Plasma amino acids were determined in 89
offenders who had committed various violent and non-violent crimes and
in 14 healthy controls.
Results. Both tryptophan and its competitors were higher
in offenders who had committed violent crimes compared both with
non-violent offenders and with controls. No difference was, however,
seen in the relationship between tryptophan and its competitors.
Conclusions. The results support the contention that
violent behaviour is related to biochemical deviations but could not
explain a possible decreased brain 5-HT activity.