A Double-blind, Placebo-controlled Study on the Effects of Combined L-Carnosine and Cognitive Training on Cognition in Schizophrenia

Compromised cognitive functioning is a core feature of schizophrenia, yet it remains a major unmet need in the treatment of schizophrenia. Current available therapeutic approaches to enhance cognition in schizophrenia - either pharmacological or non-pharmacological (for a review) have yielded, at best, only modest results with questionable retention of the cognitive benefits and generalization of the effects into functional benefit. The investigators propose a novel approach to enhance cognition in schizophrenia: combining a food supplement with cognitive training, rather than using each intervention alone.

Aim is to test the primary hypothesis that the combination of L-carnosine with cognitive training will significantly increase the performance of patients with schizophrenia on memory and learning training tasks compared to pairing cognitive training with placebo. The investigators will also test the secondary hypotheses that in the group receiving L-carnosine increased performance is due to a greater learning rate. Carnosine has antioxidant and antiglycating action and is found in food and the human body. The investigator's choice is guided by several considerations but, primarily the evidence that L-carnosine has neuroprotective effects through its antioxidant features. Briefly, the investigators propose that alterations in metabolism in several neurotransmitter systems (particularly glutamate) can both contribute to, and be modified by, oxidative stress, and therefore antioxidant administration could positively affect neurotransmitter role in synaptic plasticity, learning and memory.

Carnosine has shown some improvements in cognitive outcomes in autism (Chez et al, 2002) and schizophrenia (Chengappa et al; unpublished). Chez used oral doses of 800mg/d for 8 weeks; while the latter study used oral doses of 2000mg for 4 weeks showing positive effects. Hence this is the dose and delivery route that will be used. The investigators have opted for 4 weeks course following broadly from these two studies. Carnosine is widely available from health and food supplement shops in the UK and US retail market in highly pure form; is a naturally occurring in food and the human body; and is well-tolerated and has a benign side-effect profile, as shown from previous trials, and is therefore not associated with any potential risks.