A comparison of plasma homovanillic acid concentrations in schizophrenic patients and normal controls.

Plasma homovanillic acid concentrations, a potential index of central dopamine turnover, were examined in normal control subjects and chronic schizophrenic patients over a 12-hour period, including the period of sleep. Plasma homovanillic acid concentrations were lower in schizophrenic patients compared with normal controls at all times; however, within the group of schizophrenics, the more symptomatic patients had higher plasma homovanillic acid concentrations than the less severely ill patients. These data are consistent with a more complex role of dopamine in schizophrenia than was previously conceptualized.