Fig. 2.

a. Statistical group differences in the effect of methylphenidate on the distribution volume between controls and marijuana abusers. Methylphenidate-induced decreases in distribution volumes were stronger in controls than in marijuana abusers (p < 0.005). There were no regions where marijuana abusers showed greater decreases than controls. b. Individual distribution volume values in putamen after placebo (PL) and after methylphenidate (MP) for marijuana abusers and controls. *p < 0.05, **p < 0.005. (Figure adapted with permission from Volkow et al. 2014a, b, c)