Cognitive impairments and psychopathological parameters in patients of the schizophrenic spectrum

Cognitive impairment is a core feature of schizophrenia and it is considered by many researchers as one of the dimensional components of the disorder. Cognitive dysfunction occurs in 85% of schizophrenic patients and it is negatively associated with the outcome of the disorder, the psychosocial functioning of the patients, and non-compliance with treatment. Many different cognitive domains are impaired in schizophrenia, such as attention, memory, executive functions and speech. Nowadays, it is argued that apart from clinical heterogeneity of schizophrenia, there is probable heterogeneity in the accompanying neurocognitive dysfunction. Recent studies for cognitive dysfunction in schizophrenia employ computerized assessment batteries of cognitive tests, designed to assess specific cognitive impairments. Computerized cognitive testing permits for more detailed data collection (e.g. precise timing scores of responses), eliminates researcher's measurement errors and bias, assists the manipulation of data collected, and improves reliability of measurements through standardized data collection methods. The aims of the present study are: the comparison of cognitive performance of our sample of patients and that of healthy controls, on different specific cognitive tests, and the testing for possible association between patients' psychopathological symptoms and specific cognitive impairments, using the Cogtest computerized cognitive assessment battery. 71 male inpatients diagnosed with schizophrenia or other psychotic spectrum disorders (mean = 30.23 ± 7.71 years of age), admitted in a psychiatric unit of the First Department of Psychiatry, Athens University Medical School, Eginition Hospital (continuous admissions) were studied. Patients were excluded from the study if they suffered from severe neurological conditions, severe visual or hearing impairment, mental retardation, or if they abused alcohol or drugs. The patients' diagnoses were based on the semi-structured diagnostic interview "Diagnostic Interview for Psychosis" (DIP) and were clinically confirmed by two independent expert psychiatrists, according to the criteria of DSM-IVTM. Our healthy control group consisted of 20 healthy male participants (mean = 31.65 ± 5.90 years of age), who met the same inclusion criteria for the study as the patient group, as well as the same exclusion criteria from the study, having no history of psychiatric disorders. All statistical analyses were conducted using the statistical package SPSS.17. According to our results, healthy controls cognitively outperform our patient sample in all cognitive tests, with the differences between performances being statistically significant. Results concerning the association between psychotic symptoms and cognitive deficits of our patients indicated that hallucinations, highly organized delusions, persecutory delusions, agitation, catatonia and inappropriate affect did not associate with any subtype of cognitive deficit. Blunted affect associated significantly with response inhibition ("GoNoGo test", p = 0.007), and poor speech associated significantly with declarative memory of faces ("FMT test", p = 0.002). Moreover, psychomotor ability (non-dominant hand) associated significantly with generalized delusions ("TST test", p = 0.033), and with constricted affect ("TST test", p = 0.026). Furthermore, there was a tendency towards significance association between persecutory delusions and executive function ("CPT test", p = 0.053), inappropriate affect and declarative face memory ("FMT test", p = 0.056), and psychomotor ability and poor speech (p = 0.086).