• Plasma homovanillic acid concentrations, a potential index of central dopamine turnover, were examined in normal control subjects and chronic schizophrenic patients over a 12hour 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.
Davidson M, Davis KL. A Comparison of Plasma Homovanillic Acid Concentrations in Schizophrenic Patients and Normal Controls. Arch Gen Psychiatry. 1988;45(6):561-563. doi:10.1001/archpsyc.1988.01800300057006