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Although several studies have pointed to a possible role of interleukin 2 (IL-2) in schizophrenia (SZ), association between IL-2 and the different groups of symptoms has not been explored. The objective of this study was to investigate a possible correlation of peripheral IL-2 levels with symptoms and cognitive performance in patients with SZ. In addition, we compared the plasma levels of IL-2 between patients with SZ and healthy controls. Twenty-nine chronically medicated outpatients with SZ according to DSM-IV were compared with twenty-six healthy controls. The patients were evaluated with the Positive and Negative Syndrome Scale (PANSS), the Calgary Depression Scale for Schizophrenia (CDSS), the Clinical Global Impression (CGI) and the Global Assessment of Functioning (GAF). All the participants had blood collected into EDTA tubes by venipuncture between 9:00 and 10:00AM. Plasma concentrations of IL-2 were determined by cytometric bead array. A computerized neuropsychological battery assessed verbal learning, verbal fluency, working memory, set shifting, executive function, inhibition and intelligence. Patients with SZ had lower levels of IL-2 than healthy controls (p<0.001). In the SZ group, IL-2 levels were positively correlated with scores in the digit span test (rho=0.416, P=0.025) and intelligence (rho=0.464, P=0.011). We also found a negative correlation between IL-2 and total score in the negative subscale of PANSS (rho=-0.447, p=0.015). Our findings suggest that IL-2 may be involved in the mechanisms related to cognitive deterioration and negative symptomatology in schizophrenia.

Objective: To investigate if verbal fluency impairment in schizophrenia reflects executive function deficits or results from degraded semantic store or inefficient search and retrieval strategies. Method: Two groups were compared: 141 individuals with schizophrenia and 119 healthy age and education-matched controls. Both groups performed semantic and phonetic verbal fluency tasks. Performance was evaluated using three scores, based on 1) number of words generated; 2) number of clustered/related words; and 3) switching score. A fourth performance score based on the number of clusters was also measured. Results: Individuals with schizophrenia produced fewer words than controls. After controlling for the total number of words produced, a difference was observed between the groups in the number of cluster-related words generated in the semantic task. In both groups, the number of words generated in the semantic task was higher than that generated in the phonemic task, although a significant group vs. fluency type interaction showed that subjects with schizophrenia had disproportionate semantic fluency impairment. Working memory was positively associated with increased production of words within clusters and inversely correlated with switching. Conclusion: Semantic fluency impairment may be attributed to an inability (resulting from reduced cognitive control) to distinguish target signal from competing noise and to maintain cues for production of memory probes.

tests and outcome measures, in order to enable more pertinent comparisons across studies.

Background The trajectories of psychological distress differ between individuals, but these differences can be difficult to understand because the measures contain both consistent and situational features; however, in longitudinal studies these sources of information can be disentangled. In addition to occasion-specific features, interindividual differences can be decomposed into two sources of information: trait and carry-over effects between neighboring occasions that are not related to the trait (i.e. accumulated situational effects). Methods To disentangle these three sources of variance throughout adulthood, the consistency (trait and accumulated situational effects) and occasion specificity of nine indicators of psychological distress from the Malaise Inventory were examined in two birth cohorts, the 1958 National Child Development Study (NCDS58), and the 1970 British Cohort Study (BCS70). Results The scale was administered at ages 23, 33, 42, and 50 in NCDS58 (n = 7147), and at ages 26, 30, 34, and 42 in BCS70 (n = 6859). For each psychological symptom, more variance was consistent than occasion-specific. The majority of the consistency was due to trait variance as opposed to accumulated situational effects, indicating that an individual predisposed to be distressed at the beginning of the study remained more likely to be distressed over the whole period. Symptoms of rage were notably more consistent among males than females in both cohorts (78.1% and 81.3% variance explained by trait in NCDS58 and BCS70, respectively), and among females in the NCDS58 (69%). Conclusions Symptoms of psychological distress exhibited high stability throughout adulthood, especially among men, due mostly to interindividual trait differences.