Cognitive and Functional Subgroups in Scizophrenia

Sammanfattning: The general aim of this thesis was to explore global and specific aspects of neurocognition in a clinically representative group of schizopsychotic patients, i.e. patients with schizophrenia or related psychotic disorders, in comparison with a population of matched healthy volunteers. In Study I, 196 schizopsychotic outpatients were combined with 196 healthy volunteers into one single group, which was then divided into three subgroups of verbal learning performance based on their scores on a verbal learning test. MANOVA and discriminant function analysis were used to analyze and compare neurocognitive test profiles related to different levels of verbal learning performance among schizopsychotic patients and healthy volunteers, in order to identify the major predictors of category assignment. The results showed working memory to be related to verbal learning on all three levels of verbal learning performance and vocabulary to be related to verbal learning for the better performing patients. The study showed that despite similar capacity in verbal learning, working memory and vocabulary, the better performing schizopsychotic patients did not perform on an overall level equal to the healthy volunteers. This finding indicates retarded visuomotor processing speed, which has been suggested to be a generalised characteristic of the schizophrenic process. In Study II, the relationship between neurocognitive test performance and global assessment of functioning was studied in 195 schizopsychotic outpatients that were assigned to functional groups on the basis of their sex. A global cognition score was created based on previously presented area-under-the-curve values. Global cognition was best predicted by GAF Symptom levels in the female schizopsychotic patients, and by GAF function levels in the male patients. There was also a gender-specific difference in the neurocognitive components, indicating that executive functioning may have a greater impact on the symptom and function profiles of schizopsychotic males than on schizopsychotic females. The eventual contributions of different mediating variables are discussed.