Fig. 3: Mediating effects of trait impulsivity in the relationship between gray matter volume of the specific brain region and drug use characteristics.

a, mediating role of motor impulsivity between thalamic volume and drug use duration; (b), mediating role of motor impulsivity between thalamic volume and clinical severity. GMV, gray matter volume; MI, motor impulsivity; METH, methamphetamine; MUD, methamphetamine use disorder.