All individuals provided written informed consent. The Collaborative Genetic Study of Nicotine Dependence (COGEND) study was approved by the Washington University Institutional Review Board. The Early Methamphetamine Abstinence: fMRI and Cognition (MA fMRI); Neural Systems, Inhibitory Control, and Methamphetamine Dependence (Modafinil); Neural Systems and Risk for Adolescent Smoking (ASCC2); and Neural Correlates of Cognition, Craving and Reward Delay in Adolescent Smokers (ASCC Neural Systems) studies were approved by the University of California, Los Angeles Institutional Review Board. The Total Exposure Study (TES) was approved by the SRI International Human Subjects Committee. The Pharmacokinetics in Twins (PKTWIN), Pharmacogenetic Study of Nicotine Metabolism (588), and Smoking in Families (SMOFAM) studies were approved by the committee on Human Research at the University of California San Francisco and the Human Subjects Committee at SRI International.
