To investigate the symptom dimensions of psychosis using factor analyses/FA of lifetime symptoms of a sample of Portuguese psychotic patients.

FA of the OPCRIT items (56 signs and symptoms) of 684 patients

- Schizophrenia/Sz (73.8%), Other non-organic psychotic disorders/ONPD (6.0), Schizoaffective disorders/SzA (1.4%), Bipolar disorders/BP (18.1%) and Severe depression with psychosis/SDP (.8%) – assessed with the Diagnostic Interview for Genetic Studies.

Delusions of poverty, guilty delusions, nihilistic delusions, primary delusional perception, and somnolence, problems with appetite and weight and grandiosity were excluded from the final solution, as each were present in less than 10% of patients and did not load at any factor.

Following the Kaiser and the Cattel's Scree Plot criteria, a four factors structure was selected, which explained variance (EV) was of 60.25%. Based on items content, the meaningful four factors were denominated as follows: F1 Depression (EV 21.77%; a=.97); F2 Mania (5.72%; a=.97); F3 Delusions and hallucinations (2.97%; a=.92); F4 Disorganization and Negative symptoms (2.07%; a=.90). Mann-Whitney U tests revealed that the symptom dimensions that distinguished better between Dx categories were Delusions and hallucinations (only SDP vs. BP and Sc vs. SzA did not significantly differ) and Disorganization and Negative symptoms (only SDP vs. BP and SDP vs. ONPD did not significantly differ), with Sz patients presenting the highest scores.

This factorial structure is in accordance with other reports. Given the Schizophrenia (Sz) and Bipolar disorder (BP) heterogeneity and overlap, the present study contribute to phenotypic refinement and formulation of alternative psychosis phenotypes.