Adjunctive Glycine Treatment Improves Clinical Symptoms and Logical Memory Processing in Patients with Schizophrenia
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1
Monash University and the Alfred Hospital, Monash Alfred Psychiatry Research Centre, Central Clinical School, Australia
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2
Monash University, School of Psychology and Psychiatry, Australia
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3
University of Cambridge, Brain Mapping Unit, Department of Psychiatry, United Kingdom
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4
University of York, York Neuroimaging Centre, Department of Psychology, United Kingdom
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5
University of Newcastle, School of Psychology, Australia
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6
University of Wollongong, Illawarra Health & Medical Research Institute, Australia
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7
University of Wollongong, School of Psychology, Australia
i. Background: Typical and atypical antipsychotic medications are effective for ameliorating the positive symptoms of schizophrenia, however they have limited efficacy for negative symptoms and cognitive impairments. Cognitive abnormalities in schizophrenia are now considered a core feature of the illness and while neurocognitive dysfunction is strongly associated with functional disability, and severity of cognitive impairment is a major determinant of outcome, there are currently no accepted treatments for this symptom domain. Increasing evidence suggests that glutamatergic mechanisms may underlie the pathophysiology of schizophrenia and recent strategies to enhance cognition by targeting the glycine modulatory site of the NMDA receptor have been a focus for potential new treatments.
ii. Method: 28 outpatients with schizophrenia or schizoaffective disorder participated in a 6-week randomised double-blind placebo-controlled clinical trial with 0.4-0.8g/kg per day glycine added to their regular antipsychotic medication. Clinical assessment was conducted at baseline and week 6 using the Positive and Negative Syndrome Scale (PANSS). Auditory-verbal memory was assessed at baseline and week 6 using logical memory prose passages.
iii. Results: In the glycine group significant reductions were found in PANSS total scores (p=0.001; eta-squared=0.66) that were not observed in the placebo group (p=0.261). This glycine effect was largest for the General (p=0.003; eta-squared=0.59) and Positive (p=0.015; eta-squared=0.46) subscales but only at trend-level for the Negative (p=0.068; eta-squared=0.30) subscale. Glycine administration resulted in a trend to improve immediate logical memory (p=0.069; eta-squared=0.27) and a significant improvement in delayed logical memory (p=0.010; eta-squared=0.50), whereas placebo had no effect on logical memory processing (immediate: p=0.601; delayed: p=0.336).
iv. Discussion: These results support earlier equivocal reports that glycine effectively treats clinical symptoms of schizophrenia, and goes further to directly demonstrate a cognitive benefit of glycine using neuropsychological measures. The results highlight the potential therapeutic benefit of NMDA co-agonists in improving not only clinical symptomatology but also dysfunction in auditory-verbal logical memory in people with schizophrenia, and provide further support for the NMDA receptor dysfunction hypothesis of schizophrenia.
Acknowledgements
This research was funded by the National Health & Medical Research Council of Australia, Project Grant #502910
Keywords:
Schizophrenia,
Glycine,
logical memory,
Cognition,
Clinical Trial,
NMDAR
Conference:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference, Clayton, Melbourne, Australia, 28 Nov - 1 Dec, 2013.
Presentation Type:
Poster
Topic:
Other
Citation:
Green
AE,
Fitzgerald
PB,
Nathan
PJ,
Johnston
PJ,
Michie
PT,
Kulkarni
J and
Croft
RJ
(2013). Adjunctive Glycine Treatment Improves Clinical Symptoms and Logical Memory Processing in Patients with Schizophrenia.
Conference Abstract:
ACNS-2013 Australasian Cognitive Neuroscience Society Conference.
doi: 10.3389/conf.fnhum.2013.212.00052
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Received:
15 Oct 2013;
Published Online:
25 Nov 2013.
*
Correspondence:
Ms. Amity E Green, Monash University and the Alfred Hospital, Monash Alfred Psychiatry Research Centre, Central Clinical School, Melbourne, Australia, amity.green@monash.edu