Multiple deficit theory of schizophrenia: incidence of markers vs. symptoms.

Forty schizophrenic, 20 affective-disordered, and 40 matched normal control subjects were compared on postulated marker and symptom measures of schizophrenic deficits in: (a) affect; (b) attention; (c) proprioception; and (d) thought. The schizophrenic group was significantly more impaired on all four vulnerability markers than were the other two groups, while the schizophrenic and affective-psychotic groups showed comparable impairments on three of the psychotic symptom deficits. The incidence of multiple marker deficits was significantly greater in the schizophrenic than in the affective group. The hypothesis of independence of marker deficits was supported by the absence of any significant correlations among markers in the schizophrenic sample. The data support the theory that independent markers of schizophrenic vulnerability may potentiate schizophrenic disorders when their incidence is concurrent and at deficit levels.