A longitudinal study of the relationships between psychometric test scores, offence history and the plasma concentrations of phenylacetic and 5-hydroxyindoleacetic acids in seven inmates of a prison for the psychiatrically disturbed.

1. The plasma concentrations of phenylacetic (PAA) and 5-hydroxyindoleacetic (5HIAA) acids in seven inmates incarcerated in the Regional Psychiatric Centre (Prairies), Correctional Service of Canada, were assessed each weekday for four weeks (i.e., 20 samples each). Psychometric assessments for hostility, anger, depression and anxiety were also performed daily. Mean differences between subjects in psychometric and biochemical measures were subjected to tests of statistical significance. 2. The subject who was clearly most aggressive by offence history/institutional behavior scored significantly highest on scales of anger and hostility and significantly lowest with respect to PAA concentration. It was concluded that PAA may be a trait marker for aggression. 3. Plasma 5HIAA concentrations were invariant between subjects. 4. The psychometric measures were intercorrelated, thus confounding the variables of interest. They also varied little, proving insensitive to subtle mood changes.