Bilateral skin conductance activity, clinical symptoms and CSF monoamine metabolite levels in unmedicated schizophrenics, differing in rate of habituation.

Bilateral skin conductance (SC) and heart rate (HR) were recorded for 18 RDC-diagnosed unmedicated recently admitted psychotic patients (13 schizophrenic and 5 paranoid) and for age- and sex-matched controls, during rest and tone stimulation (85 dBA, 1000 Hz, 1 sec duration and 0.25 msec rise time). Schizophrenics had more SC spontaneous fluctuations and faster HR, indicating higher arousal. SC spontaneous fluctuations were more frequent in left hand and showed an increasing trend over the session. Several SC measures indicated higher responsivity and a more irregular responding pattern in schizophrenics. These patients had higher levels of the noradrenaline metabolite (MHPG). Paranoid psychotic patients had a more stable SC habituation course than controls, and higher levels of the dopamine (HVA) and serotonin metabolites (5-HIAA). Schizophrenic nonhabituators had fewer positive psychotic symptoms than habituators, suggesting that poor habituation is not due to interference by symptoms. It may be related to higher arousal, or to deficient information processing.