Identification of symptomatologic patterns common to major psychoses: proposal for a phenotype definition

Our study was designed to identify the underlying symptomatologic structure common to major psychoses as a preliminary step for a phenotype definition. We investigated 1,004 inpatients affected by mood disorders or the schizophrenia spectrum (DSM-III-R) using the OPCRIT checklist (operational criteria checklist for psychotic illness). Symptomatologic structure was extracted by factor analytic techniques and factor scores were first obtained on 500 subjects. A CFA (confirmatory factor analysis) was then conducted on the remaining 504 subjects to evaluate fitness of the model. We identified four factors: excitement, depression, disorganization, and delusion. These factors accounted for 54.6% of the total variance of the OPCRIT checklist symptomatologic subset of 38 items. CFA indices showed a good fit for the model. We identified symptomatologic structures common to major psychoses. The factors identified were confirmed in an independent sample. Two of these symptomatologic structures are partially overlapping with categorical diagnoses (excitement and depression), and two constitute independent psychopathologic traits (delusion and disorganization). The use of "factor-derived scores" in genetic research may add a dimensional definition to the diagnostic subdivision of major psychoses.