Plasma homovanillic acid concentration and the severity of schizophrenic illness.

Concentrations of plasma homovanillic acid before treatment were highly correlated with global severity of illness in schizophrenic patients, both before and after treatment. In contrast, a fixed dose of haloperidol did not affect those concentrations. Thus, in patients with a diagnosis of schizophrenia, plasma homovanillic acid may reflect the severity of illness, but not be influenced by short-term pharmacological perturbations by neuroleptics.