Background: Working memory deficits are considered endophenotypes for schizophrenia. Therefore, they are present in ill subjects prior to the onset of the disorder, during the evolution of the disorder as well as in healthy relatives.
Aims: The purpose of this study was to examine the working memory of first episode schizophrenia patients (FEP) and their healthy siblings. In addition, we examined the relationship between the duration of untreated psychosis (DUP), the global functioning, symptoms, and cognitive function in first episode patients.
Methods: 49 first episode inpatients, 25 healthy siblings and 41 healthy volunteers were recruited. Patients were diagnosed using the SCID for DSM-IV disorders, assessed with the PANSS and Global Assessment of Functioning scale (GAF). DUP was calculated by means of multiple-source interviews, with patients and relatives. The Rey Auditory Verbal Test (RAVT), the Paired Associates Learning Test (PAL), the Spatial Span Test (SSP) and the Spatial Working Memory Test (SWM) from the CANTAB were administrated to all subjects.
Results: Patients had an average duration of untreated psychosis of 303.10 days. The overall performance of first episode schizophrenia patients was significantly lower compared to healthy individuals on all cognitive tasks, with the exception of the errors on the SSP. Healthy siblings had intermediate scores; they performed similar to controls on some tasks (RAVLT - retroactive inference, delayed recall, recognition, PAL first trial score and on the number of completed stages), and lower on others (RAVLT - immediate memory, total learning, proactive inference, PAL total errors and the stages completed on the first trial).
Discussion and conclusions: A significant correlation between the DUP and the PANSS general symptoms scores and low general function could be established. However, there were no significant correlations between DUP and cognitive tasks.
Keywords: working memory, first episode of schizophrenia, siblings, CANTAB
The cognitive dimension of schizophrenia remained obscured by the disorder's positive, negative and disorganized dimensions. Cognitive disorders in schizophrenia are being reconsidered: they have been thought to be present years before the onset of the frank disease, endurable, progressive, and less responsive to treatment (Eastvold et al., 2007). There is growing awareness that neurocognitive impairments are core features of schizophrenia (Gur et al., 2007) that are independent of clinical symptoms and linked to functional outcomes (Gonzalez-Blanch et al., 2007). Furthermore, they are considered intermediate phenotypes or cognitive endophenotypes (Gottesman & Gould, 2003) that are identifiable and measurable by laboratory based methods. Although they are expressed as subtle signs, they represent a characteristic of the disorder and are biochemical, neuroanatomical, and neuropsychological endophenotypes (Bratti & Bilder, 2006).
The features of endophenotypes include: signs or symptom clusters that are considered vulnerability markers associated with the illness. They are heritable with familial co-segregation and are present in unaffected relatives. They are independent of the evolution of the disease and to positive or negative symptoms. In addition, they are stable over time and relate directly to the functional outcome (Cornblatt et al., 2007) and are less influenced by treatment (Gottesman & Gould, 2003).
Neurocognitive endophenotypes include: attention deficits (Cornblatt & Malhotra, 2001), working memory impairments (Cannon et al., 2000, Tuulia- Henriksson et al., 2003), antisaccadic eye movements (Ettinger et al., 2006), neurological soft signs, P50 prepulse inhibition (Hong et al., 2007).
A great amount of research has been dedicated to the various neurocognitive deficits in chronic schizophrenia. But these may …