Randomized controlled trial of a gluten-free diet in patients with schizophrenia positive for antigliadin antibodies (AGA IgG): a pilot feasibility study

Background: Approximately one-third of people with schizophrenia have elevated levels of anti-gliadin antibodies of the immunoglobulin G type (AGA IgG) ­ a higher rate than seen in healthy controls. We performed the first double-blind clinical trial of gluten-free versus gluten-containing diets in a subset of patients with schizophrenia who were positive for AGA IgG. Methods: In this pilot feasibility study, 16 participants with schizophrenia or schizoaffective disorder who had elevated AGA IgG (≥ 20 U) but were negative for celiac disease were admitted to an inpatient unit for a 5-week trial. All participants received standardized gluten-free meals and were randomized in a double-blind fashion to receive a shake containing 10 g of gluten flour or 10 g of rice flour each day. Participants were rated for psychiatric, cognitive and gastrointestinal symptoms at baseline and endpoint. Results: Of the 16 participants, 14 completed the 5-week trial (2 discontinued early for administrative reasons). Compared with participants on the gluten-containing diet, participants on the gluten-free diet showed improvement on the Clinical Global Impressions scale (Cohen d = ­0.75) and in negative symptoms (Cohen d = ­0.53). We noted no improvement in positive or global cognitive symptoms, but did observe an improvement in attention favouring the gluten-free diet (Cohen d = 0.60). Robust improvements in gastrointestinal adverse effects occurred in the gluten-free group relative to the glutencontaining group. Adverse effects were similar between groups. Limitations: This study was limited by its small sample size; larger studies are needed. Conclusion: This feasibility study suggests that removal of gluten from the diet is associated with improvement in psychiatric and gastrointestinal symptoms in people with schizophrenia or schizoaffective disorder.

Anticipatory vs. consummatory pleasure: what is the nature of hedonic deficits in schizophrenia?

Recent research has distinguished between anticipatory and consummatory pleasure. In the current study, we examined the psychometric properties of the Temporal Experience of Pleasure Scale (TEPS) to determine whether reliability and validity findings reported in previous research replicate in an additional sample of schizophrenia patients. Participants included 86 individuals with schizophrenia and 59 demographically matched healthy controls. Inconsistent with previous research, patients differed from controls in their reports of consummatory (TEPS-CON), but not anticipatory (TEPS-ANT) pleasure. We also failed to replicate some important correlational findings reported in previous research indicating relationships between the TEPS-ANT subscale and external validators. Analyses of the stability of the TEPS subscales were conducted in a sub-group of patients (n=19), and indicated excellent stability for the TEPS-CON (ICC (intraclass correlation coefficient)=0.93), but somewhat lower stability for the TEPS-ANT subscale (ICC=0.74). These findings suggest that additional studies are needed using the TEPS, as well as other measures, to determine the nature of anhedonia in individuals with schizophrenia.

The MATRICS Consensus Cognitive Battery (MCCB): clinical and cognitive correlates.

The purpose of this study was to examine the cognitive and clinical correlates of the MATRICS Consensus Cognitive Battery (MCCB) which was originally developed to be an endpoint for cognitive enhancement clinical trials. In a sample of 117 people with schizophrenia and 77 healthy control participants we found the following: a) the MCCB was highly sensitive to the type and level of impairment typically observed in schizophrenia, b) the MCCB composite score was highly correlated with WASI Estimated Full Scale IQ score, c) that the MCCB domain scores were generally moderately-highly intercorrelated, d) that MCCB performance was minimally related to clinical symptom type and severity, and e) the MCCB is sensitive to employment status with better performance in employed vs. unemployed patients. These data support the validity of the MCCB as a sensitive measure of cognitive impairment in schizophrenia and suggest that MCCB performance is relevant for functional outcome. The data also suggest that the MCCB domain scores may offer limited resolution on discrete cognitive functions.