To summarize, NAA levels were statistically lower in the thalamus only in AUD-R and AUD-lost relative to controls, raising the possibility that low NAA levels present a liability for relapse. The absence of a more general AUD group effect and a more salient effect on frontal white matter NAA levels may be related to recency of drinking, with longer abstinence associated with higher levels of NAA in both frontal white matter and thalamus. Cho levels were also lower in AUD individuals with more recent drinking and also those with history of stimulant use, but higher in those that reported binge drinking and those with a longer length of dependence. Potential group differences thus become obscured because competing mechanisms can influence in vivo Cho levels. Together, these results caution against over-interpretation of MRS research study results, especially of the complex signal composed of multiple choline-containing compounds associated with different underlying mechanisms (e.g., Hellem et al., 2015; Zahr et al., 2014). This study also highlights the need to recognize alcoholism-related factors underlying heterogeneity and contributing to variability in patterns of abnormalities observed in alcoholism.
