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The influence of stimulation frequency and stimulus intensity on the auditory evoked potential components N1 and P2 was investigated in schizophrenic and major depressive patients. The findings in the patients were compared with those in normal controls. At a high stimulation frequency the amplitude of N1 was enhanced in both schizophrenic and major depressive patients; the latency of N1 increased only in the schizophrenic patients. These changes may be related to impairments of auditory input control and processing in these diseases. In the schizophrenic patients, P2 latency was prolonged under treatment with high-potency neuroleptic drugs.

From the Bonn study including 502 patients followed up an average 22.4 years after onset of schizophrenic disease diagnosed according to the criteria of K. Schneider, we selected 113 cases of schizo-affective, schizophreniform, and cycloid psychoses in accordance to the definitions given by Kasanin, Retterstøl, Angst, and Leonhard. These psychoses have a better prognosis than the whole sample: characteristic residues are seen more rarely, complete remissions and noncharacteristic residues more frequently. This group of psychoses differs from the whole sample in the hereditary taint, too: the morbidity risk with affective psychoses and with schizophrenic psychoses in first- and second-degree relatives is higher than in the total sample of the Bonn study. In spite of the better prognosis and other differences described in the paper, we believe that these results do not justify the classification of schizo-affective and related disorders as an independent disease group. Between these different subtypes of schizophrenia only a differential typology and not a differential diagnostic is possible.

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