Vulnerability and schizoaffective psychosis: a two-factor model.

Remitting illness such as affective or schizoaffective disorder is appropriately described by a vulnerability model. Clinical evidence is reviewed here to clarify the relationship between the affective-disorder-like and schizophrenia-like symptoms in a schizoaffective episode. A model is proposed which treats vulnerability to schizoaffective and schizophreniform psychosis as the result of two factors. The first factor is vulnerability to an episode of psychotic illness characterized by psychomotor and vegetative activation. The second is vulnerability to cognitive disturbance in response to increased activation. The relationship between stress and increased activation may be mediated by dopaminergic systems; this relationship is probably specific neither to etiology nor to diagnosis. The relationship of cognitive symptoms to episodes of activation is unclear. The model presented here may help organize and interpret research in this area, especially as traditional research designs which emphasize comparisons between diagnostic groups may not address these questions adequately.