Substance use disorders (SUDs) are characterized by a compulsion to seek and consume one or more substances of abuse, with a perceived loss of control and negative emotional state. Repeated use of a substance results in synaptic and morphological changes, secondary to toxicity and SUD pathology in the dopamine striato-thalamo-cortical and limbic pathways. These neuroadaptations seem to vary between studies, which could be related to divergent effects of substances, consumption severity or other unknown factors. We therefore identified studies investigating the effects of SUDs using volumetric whole-brain voxel-based morphometry (VBM) in gray (GM) and white matter (WM). We performed a systematic review and meta-analysis of VBM studies using the anatomic likelihood estimation (ALE) method implemented in GingerALE (PROSPERO pre-registration CRD42017071222). Fifty studies met inclusion criteria and were included in the final quantitative meta-analysis, with a total of 538 foci, 88 experiments and 4370 participants. We found convergence and divergence in brain regions and volume effects (higher vs lower volume) in GM and WM depending on the severity of consumption pattern and type of substance. Convergent pathology was evident across substances in GM of the insula, anterior cingulate cortex, putamen, and thalamus, and in WM of the thalamic radiation and internal capsule bundle. Divergent pathology between occasional use (cortical pathology) and addiction (cortical-subcortical pathology) provides evidence of a possible top-down neuroadaptation. Our findings indicate distinctive brain morphometry alterations in SUDs, which may inform our understanding of disease progression and ultimately therapeutic approaches.MANUSCRIPT Pando-Naude, Victor Garza-Villarreal, Eduardo A.MANUSCRIPT Pando-Naude, Victor Garza-Villarreal, Eduardo A. 5 terms for articles published to the end of July 2018. No restrictions were placed on study design, but in order to be eligible for inclusion, the studies must have reported whole-brain VBM analyses. Screening and data extraction were performed using the Covidence tool 31 . The main outcome to extract was any change in gray and/or white matter analyzed using VBM, in stereotactic coordinates, comparing a substance user group and a healthy control group (details in Supplementary information).
Quality assessment of MRI studies.Criteria for MRI quality reporting was selected from a set of guidelines for the standardized reporting of MRI studies [32][33][34] . Such guidelines dictate a more consistent and coherent policy for the reporting of MRI methods to ensure that methods can be understood and replicated.
Analysis and meta-analytic technique.Statistically significant foci from between-group contrasts were extracted and recorded for each study. If necessary, coordinates were converted from Talairach coordinates to MNI space using the Lancaster transform (icbm2tal) incorporated in GingerALE (www.brainmap.org/). All metaanalyses were performed using anatomic likelihood estimation (ALE), implemented ...