“nicotine,” “cocaine,” “methamphetamine,” or “cannabis.” Model 2 did not permit inclusion of individuals who were dependent on more than one substance. In both models, MRI site was entered as a random factor, and sex, age, and total intracranial volume were included as covariates. Further analyses were performed to disconfirm the existence of a site-by-diagnosis interaction (see the Supplemental Methods section in the online supplement).
