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Comment & Response |

The Problem of Spurious Correlations Between Pairs of Brain Metabolite Values Measured in the Same Voxel With Magnetic Resonance Spectroscopy

Richard Maddock, MD1
[+] Author Affiliations
1Imaging Research Center, Department of Psychiatry, University of California–Davis, Sacramento
JAMA Psychiatry. 2014;71(3):338-339. doi:10.1001/jamapsychiatry.2013.4343.
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To the Editor The article by Kraguljac and colleagues1 presents a potentially important finding on the association between hippocampal glutamate levels and hippocampal morphology. However, one aspect of the article requires correction. The authors report a significant positive correlation (r = +0.39) between N-acetylaspartate (NAA)/creatine (Cr) and glutamate and glutamine (Glx)/Cr in normal participants that is lost in patients with schizophrenia (r = −0.19). Unfortunately, using zero correlation as the null hypothesis here is incorrect because Glx/Cr and NAA/Cr are not independent numbers. Both include the Cr value in their denominator.


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March 1, 2014
Nina V. Kraguljac, MD; Gary R. Cutter, PhD; Charity Morgan, PhD; Adrienne C. Lahti, MD
1Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham
2Department of Biostatistics, University of Alabama at Birmingham
JAMA Psychiatry. 2014;71(3):339-340. doi:10.1001/jamapsychiatry.2014.22.
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