 Functional genetic polymorphisms have been identified that influence the morphology and function of brain regions that have been implicated in addictive and neuropsychiatric disorders. This protocol aims to integrate genotyping with both structural and functional brain imaging to investigate the impact of specific functional polymorphisms on morphology and function of the amygdala and the hippocampus and on behavior mediated by these brain regions. Functional polymorphisms of the BDNF, SLC6A4, and DISC1 genes will be studied, as these are logical candidates to influence variability in brain morphology and function. The overall hypothesis is that variation in morphology and function of the amygdala and the hippocampus is explained, at least in part, by specific genotype differences. 