The complex relationships between executive functions and positive symptoms in schizophrenia

Background. Relationships between performance on various tests of executive functions and positive symptoms, especially delusions and hallucinations, have not been found consistently. This may be related to method of rating symptoms, to possible interactions between them, as well as to the low specificity of the cognitive test measures used. In this study, we have investigated the relationships between different aspects of positive symptomatology and several executive subprocesses. Method. Stable schizophrenia patients (n = 96) were assessed for disorganization, delusion and hallucination symptoms rated from the Scale for Assessment of Positive Symptoms and the Scale for Assessment of Negative Symptoms. Interference sensitivity, inhibition and flexibility were assessed using the Wickens paradigm. The relationships between symptom dimensions as well as with cognitive and other potentially confounding variables were assessed using Pearson correlations and (simple and partial) stepwise regressions. Results. Generally consistent with the cognitive constructs used to account for positive symptoms, the results indicated relationships between delusions, disorganization and inhibition, and between hallucinations and interference sensitivity. However, these relationships appeared more complex than expected, with some being dependent on interactions between symptoms. Conclusions. These results suggest: (i) that the global measures usually employed may not be appropriate for demonstrating specific relationships between symptoms and executive functions and (ii) that it is necessary to take into account the interactions between positive symptoms as well as with other factors to reveal these relationships.