Possible explanations for study result differences include heterogeneity of the AUD populations studied, voxel placement (e.g., frontal white vs. frontal gray matter) and the quantification in earlier studies of metabolites as ratios (relative to tCr) (e.g., Bendszus et al., 2001; Jagannathan et al., 1996; Seitz et al., 1999) rather than as absolute concentrations. The potential for drinking variables (e.g., binge-like drinking, length of dependence as noted in this study) or for AUD diagnosis (e.g., Durazzo et al., 2010; Meyerhoff et al., 2004) to modulate tCr levels might have obfuscated results in other studies in which metabolites are expressed as ratios to tCr.
