[Reduced serotonin levels in platelet-free plasma of adolescents with externalizing behaviour problems]

A serotonergic dysfunction, in particular a reduced serotonergic neurotransmission in the frontal cortex and limbic brain regions, has been discussed in connection with the aetiology of aggressive and impulsive behaviour. Assessment of the activity in the central serotonergic system in children and adolescents is limited due to its technical complexity and ethical restrictions. Therefore, peripheral serotonergic parameters have been used as a model to obtain deeper insight into central serotonergic functions. The aim of this investigation is to examine the significance of plasma serotonin measurement with regard to behavioural problems in adolescents at risk for psychopathology.

Within the framework of a prospective longitudinal study of children at risk, serotonin levels in platelet-free blood plasma were measured in a group of n = 10 adolescents aged 15 years with persistent externalizing behaviour (T-score > or = 60 on the "Externalizing Problems" scale of the CBCL) and in a control group of n = 20 mentally undisturbed adolescents. Groups were matched according to age and gender. Externalizing behaviour was assessed by means of a parent questionnaire, the Achenbach Child Behavior Checklist (CBCL).

Significantly lower levels of plasma serotonin were found in adolescents with persistent behaviour problems than in the control group. Significant negative correlations between serotonin levels and the CBCL scales "Aggressive Behavior" and "Externalizing Problems" were obtained for the total sample.

Earlier findings that described a serotonergic deficit as a key mechanism in the manifestation of aggressive and antisocial behaviour are confirmed for adolescents at risk taken from a community sample.