Are paranoid schizophrenics biologically different from other schizophrenics?

Two studies were undertaken to verify the presence of lowered platelet monoamine oxidase activity in chronic schizophrenia. In the first study, a retrospective chart analysis, the mean platelet activity of patients with chronic schizophrenia (7.73+/-0.64 nmol of benzylaldehyde product per 10(8) platelets per hour [S.E.M.]) differed significantly from that of normal controls (12.13+/-0.2, P less than 0.001). Chronic paranoid schizophrenics (4.81+/-0.46) differed significantly from chronic nonparanoid schizophrenics (8.6+/-0.75, P less than 0.03). A separate prospective study confirmed significantly lower values for monoamine oxidase activity in chronic schizophrenic patients diagnosed as paranoid (5.97+/-1.17) or as having secondary paranoid features (6.28+/-0.71) as compared to chronic nonparanoid schizophrenics (9.81+/-0.87, P less than 0.001). Chronic paranoid schizophrenia may be a separate disorder from the other chronic forms of schizophrenia, and this difference may be related, at least in part, to biochemical characteristics.