Category fluency in schizophrenia: opposing effects of negative and positive symptoms?

INTRODUCTION: Category fluency is associated with speed-, executive- and semantic impairments in schizphrenia. It has traditionally been linked to negative symptoms, whereas the relation to positive symptoms is mixed. Associations to the consensus negative, positive and disorganisation factors have not been analysed before.

METHODS: Animal fluency was administered to 81 patients with schizophrenia. Measures of overall performance and applied strategies were analysed in relation to the Wallwork five-factor PANSS-model.

RESULTS: Negative and disorganisation symptoms were negatively related to overall fluency performance. Positive symptoms were positively related to overall performance when controlling for disorganisation symptoms. Negative symptoms were related to fewer switches, less repetitions, less single animals intrusions, and both less rare and common animals. Positive symptoms were related to more effective retrieval of sub-category exemplars following a sub-category title, whereas there were no relation between symptoms and exemplars when the title was not retrieved. The Beta values of negative and positive symptoms were opposite.

CONCLUSION: This is the first study showing that positive symptoms are related to increased fluency performance when disorganisation is controlled for. Like previous studies, negative symptoms were found to depress fluency. Strategy measures indicated that negative symptoms predispose for rigidity, whereas positive symptoms facilitate more efficient associative pathways.