The aim of the current study was to explore the changing interrelationships among clinical variables through the stages of schizophrenia in order to assemble a comprehensive and meaningful disease model.

Twenty-nine centers from 25 countries participated and included 2358 patients aged 37.21 ± 11.87 years with schizophrenia. Multiple linear regression analysis and visual inspection of plots were performed.

The results suggest that with progression stages, there are changing correlations among Positive and Negative Syndrome Scale factors at each stage and each factor correlates with all the others in that particular stage, in which this factor is dominant. This internal structure further supports the validity of an already proposed four stages model, with positive symptoms dominating the first stage, excitement/hostility the second, depression the third, and neurocognitive decline the last stage.

The current study investigated the mental organization and functioning in patients with schizophrenia in relation to different stages of illness progression. It revealed two distinct “cores” of schizophrenia, the “Positive” and the “Negative,” while neurocognitive decline escalates during the later stages. Future research should focus on the therapeutic implications of such a model. Stopping the progress of the illness could demand to stop the succession of stages. This could be achieved not only by both halting the triggering effect of positive and negative symptoms, but also by stopping the sensitization effect on the neural pathways responsible for the development of hostility, excitement, anxiety, and depression as well as the deleterious effect on neural networks responsible for neurocognition.

Most neuropsychological batteries, especially those most often used, are unsuitable for the assessment of patients with severe dementia. The Severe Impairment Battery (SIB) was developed for the evaluation of preserved cognitive functions in these patients. The aim of this study was to formulate a Greek version of the SIB and to conduct a first assessment of its use of patients with mild, moderate, or severe Alzheimer's disease (AD), compared to the Mini-Mental State Examination (MMSE).

A convenience sample of 42 dementia patients according to DSM-IV-TR criteria and 23 healthy participants was selected. Patients were assessed twice using a Greek translation of the SIB and the Greek version of MMSE. Patients were divided into three severity groups based on grouped by Clinical Dementia Rating (CDR) score and the SIB and MMSE scores were compared.

The validity of the SIB was confirmed by evaluating the correlation coefficients between the SIB and Greek-MMSE, grouped by CDR, which were found to be significant. Cronbach's α for the total SIB score and each subscale score showed high significance, and the item-total correlation for each subscale was also acceptable. The test-retest correlation for the total SIB score and subscale scores were significant. The total SIB score and subscale scores were examined according to CDR.

The Greek SIB is reliable and valid in differentiating patients with moderate or severe dementia, whereas MMSE loses sensitivity due to a floor and ceiling effect.