Neuroleptic effects on autonomic activity in schizophrenia: between-group and within-subject paradigms and comparisons with controls.

Effects of fluphenazine on electrodermal activity (EDA) and heart rate (HR) were studied in patients with schizophrenia and normal control subjects during rest periods, presentation of innocuous tones, and a reaction time (RT) task. Two types of analyses were used: (1) between-group analyses-patients taking placebo were compared with patients taking fluphenazine and with control subjects using only data from the first test session; and (2) within-subject analyses-the same patients were tested when taking fluphenazine and when taking placebo. Results showed higher resting EDA and HR and smaller increments to task performance in placebo patients than in control subjects. Fluphenazine attenuated EDA levels but not the tonic response. Fluphenazine attenuated the HR response but did not affect HR level. Placebo patients were electrodermally hyporesponsive to the RT stimuli but not to simple tones. Fluphenazine markedly attenuated responsivity to simple tones but it attenuated responsivity less for RT stimuli. Testing medicated patients may thus produce misleading results with respect to many, but not all, purported autonomic markers of diagnosis in schizophrenia studies.