Sex Differences in Neuropsychological Functioning Among Schizophrenia

Sex Differences in Neuropsychological Functioning Among Schizophrenia Patients

The researchers began this research with the premise that there may be gender-based difference in cognition among schizophrenia patients, though they acknowledged that prior research gave conflicting information about which results to expect. Some prior researchers had found that male schizophrenia patients experienced greater levels of cognitive impairment than female schizophrenia patients, while other studies had found no gender-based difference in cognitive functioning. Regardless of level of cognitive impairment, women with schizophrenia are much more likely to have positive outcomes than men with schizophrenia. This is an interesting issue, because there is an established difference in cognition in healthy men and women. Specific neurocognitive deficits appear to impact community functioning, which is one of the significant impairments experienced by schizophrenia patients attempting to interact with the outside world. In prior studies, community functioning was determined to be related to verbal memory, verbal fluency, and executive functioning, and other areas where healthy women tend to outperform healthy men. In fact, the researchers acknowledged that healthy men tend to outperform women in tests requiring visuospatial skills, while women tend to perform better than men on tests of verbal abilities. Despite these known existing differences in the healthy population, prior examinations of cognitive differences in male and females with schizophrenia have assumed the same baseline starting point for both genders.

To examine these differences, the researchers looked at an experimental group of 94 patients who had been diagnosed with schizophrenia using DSM-IV criteria and confirmed by the Greek version of the Mini International Neuropsychiatric Interview. The group was unequally composed of men and women, with 56 men and 38 women. Everyone in the experimental group was on antipsychotic medication and stable at the time of the experiment. The control group was 62 healthy adults, equally composed of 31 men and 31 women. Both groups were given a wide variety of neuropsychological tests that assessed their cognitive abilities, including: auditory attention (Digit Span forward and Spatial Span forward), abstraction (Wisconsin Card-Sorting Test: categories and perserverative errors), inhibition (Trail-Making Test Part B / Stroop Colour-Word Test), fluency (Design Fluency / Verbal Fluency Test: semantic and phonological), verbal learning and memory (Word List Learning Test: learning on fifth presentation, immediate free recall, immediate cued recall, delayed free recall, delayed cued recall, recognition), visual memory (Rey-Osterrieth Complex Figure Test: immediate recall, delayed recall, recognition), working memory (Digit Span backward and Spatial Span backward), visuospatial skills (Rey-Osterrieth Complex Figure test copy / Hooper Visual Organization Test), and psychomotor speed (Trail-Making Test Part A).

When looking at the results, it is important to note that the experimental and control groups varied in educational levels, a factor that was considered in the analysis, but that might have an impact on the results. The results revealed that, overall, the experimental group was significantly impaired in most of the assessed cognitive domains, but not in psychomotor speed. There were gender differences in both the control and experimental groups, in so far as the women outperformed the men in verbal learning and memory in both groups. Therefore, female schizophrenics did, as a group, have a cognitive advantage over male schizophrenics in those two areas.

The research has several interesting implications for treatment and outcomes in schizophrenics. First, the patients with schizophrenia, as a group, demonstrated cognitive impairment despite the fact that the group was considered clinically stable and all were on anti-psychotic medications. This suggests an underlying cognitive disorder that is somehow distinct from the psychotic symptoms that frequently characterize schizophrenia and that is not responsive to traditional treatments for schizophrenia. The authors do not discuss this factor in depth in the article, but it is worth noting given that all of the patients were considered stable at the time of the test; it might provide a means for diagnosis and testing. Given suggestions that schizophrenia may be a long-term but not life-long disease, tests for cognitive functioning might be a good way of determining whether or not a patient is able to be weaned off of antipsychotic medications. On the other hand, the fact that all of the experimental subjects in the group were on antipsychotic medications certainly makes it difficult to know whether the group difference in cognitive functioning compared to the control group was attributable to the schizophrenia or the medications used to treat the schizophrenia.