Gray matter abnormalities in cocaine versus methamphetamine-dependent patients: a neuroimaging meta-analysis

Background: Voxel-based morphometry has been used to explore gray matter alterations in cocaine and methamphetamine dependence. However, the results of this research are inconsistent. Objectives: The current study meta-analytically examined neuroimaging findings of all studies published before 2014 using the Anisotropic Effect-Size Signed Differential Mapping (ES-SDM). Methods: Independent investigators searched four major databases for relevant neuroimaging studies involving cocaine and methamphetamine dependence. Nine cocaine and four methamphetamine studies met inclusion criteria. Results: Results indicated that cocaine- and methamphetamine-dependent patients share overlapping regional gray matter abnormalities compared to healthy controls. However, subgroup analysis showed some regional differences; with methamphetamine showing more prominent reductions in the left superior temporal gyrus and the right inferior parietal lobe. Reductions in the right insula and the left superior frontal gyrus were more prominent in cocaine dependence. Moderator analyses indicated that with longer use, cocaine is associated with reductions in the right hippocampus, right middle temporal gyrus, and right inferior frontal gyrus, while methamphetamine is associated with reductions in the left precentral gyrus and the right supramarginal gyrus. Conclusion: These findings indicate that cocaine and methamphetamine dependence are significantly and differentially associated with gray matter abnormalities. Results also point to possible gray matter recovery after abstinence from methamphetamine. Although the sample size was adequate, these findings should be considered preliminary and analyses should be revisited with additional primary research focusing on long or short-term duration of use, as well as the length of abstinence.