Peripheral serotonin measures in prepubertal psychiatric inpatients and normal children: Associations with suicidal behavior and its risk factors

Background: This study reports relationships between suicidal behavior and its risk factors in prepubertal children and whole blood and platelet serotonin-related measures. Methods: Seventy-five prepubertal psychiatric inpatients including 23 (30.7%) nonsuicidal, 32 (42.7%) with suicidal ideation, and 20 (26.6%) with a suicide attempt were compared to 35 normal prepubertal controls with regard to platelet serotonin content serotonin-amplified platelet aggregation, and whole blood tryptophan. Results: Mean whole blood tryptophan content was significantly lower among inpatient children,vith a recent suicide attempt than among normal controls or inpatients,vith suicidal ideation (F = 3.94, df = 3.54, p less than or equal to .01). Inpatient children with a mood disorder had significantly higher platelet serotonin content than inpatients,without a mood disorder (F = 3.86, df = 2,80, p less than or equal to .03), Racial/ethnic differences were also observed for inpatients and normal controls, with whites having significantly lon er levels of platelet serotonin (expressed as ng/mL blood or ng/10(9) platelets) than blacks or Latinos. Blacks had significantly higher levels of whole blood tryptophan than other racial/ethnic groups. Conclusions: The results suggest that whole blood tryptophan and platelet serotonin content should be studied for their predictive validity as risk factors for suicidal behavior in youth while controlling for racial/ethnic differences. (C) 1998 Society of Biological Psychiatry.