In addition to the changes in the polar regions, there are also changes in the medial temporal cortex, which is one of the structures often reported to be associated with cannabis addiction and where we find a strong bilateral decrease in gray matter volume in the population of regular cannabis users. Such a pattern of atrophy has been also described in other forms of addiction such as alcohol addiction (Mechtcheriakov et al, 2007), but not in heroin users (Denier et al, 2013). However, other patients with severe, non-toxic, behavioral addiction such as pathological gambling (Levine et al, 2005) do not present the same form of atrophy, suggesting that temporal atrophy is indeed associated with cannabis consumption rather than with addictive behavior itself. Despite the fact that the neurobiological interpretation of this volume reduction is still unclear, studies on rodents give some clues on this point. Scallet et al (1987) found a THC-induced decrease in the mean volume of hippocampal neurons and a 44% reduction in the number of synapses up to 7 months after exposure. Functional and structural variations in
