When comparing gray matter volume between groups, we find that significant clusters showing a lower gray matter volume in regular cannabis users compared with occasional ones are located bilaterally in the temporal pole and in the parahippocampal gyrus. Additional clusters cover the left insula and the left orbitofrontal cortex (Figure 1). In contrast, three cerebellar clusters show the opposite behavior, with increased gray matter volume. Coordinates of the centers of gravity of the significant clusters are reported in the Montreal Neurological Institute (MNI) space and are summarized in Tables 2 and 3.
