Cerebrospinal fluid levels of phenylacetic acid in mental illness: behavioral associations and response to neuroleptic treatment.

Cerebrospinal fluid levels of phenylacetic acid (CSF PAA) were obtained from normal controls and from drug-free psychiatric inpatients (schizophrenia, major depression, mania, and schizoaffective disorder). Post-treatment CSF PAA levels were obtained from 16 patients after 4 weeks of neuroleptic treatment. Phenylacetic acid levels were higher in women and were significantly correlated with age. There were no differences in CSF PAA levels between the various diagnostic groups and no difference between the paranoid and the nonparanoid subtypes of schizophrenia. CSF PAA was significantly correlated with several measures of psychopathology, especially the Brief Psychiatric Rating Scale hostility/suspiciousness factor. Neuroleptic treatment did not result in significant PAA changes. These findings are discussed in light of the amphetamine-like role ascribed to phenylethylamine, the precursor of PAA.