Growth hormone response to clonidine in neuroleptic-free patients with multidiagnostically defined schizophrenia

The role of α₂-adrenergic receptor sensitivity in schizophrenia was examined by measuring growth hormone (GH) response after the intravenous administration of clonidine (1.3 μg/kg) in 26 healthy control subjects and 26 neuroleptic-free, acutely psychotic patients with at least 1 out of 11 possible diagnoses of schizophrenia derived from a multidiagnostic psychopathological assessment. GH responses were significantly (0.01) lower than control values in schizophrenias defined by E. Bleuler, M. Bleuler, Schneider, Langfeldt, Taylor and Abrams, and Cloninger, but not in DSM-III, World Health Organization, Feighner, Kraepelian, and Research Diagnostic Criteria (RDC) schizophrenias. Eight patients with RDC schizoaffective disorder also had a blunted response. However, there were no correlations with any symptom measures. There were no differences between paranoid and nonparanoid patients, although there was a significant difference between nonparanoid patients and control subjects. These findings support the presence of noradrenergic dysfunction in some patients within the schizophrenia syndrome, possibly those whose illnesses have an affective component. The study also illustrates the need for simultaneous investigation of several different sets of diagnostic criteria for schizophrenia in neurobiological research.