In all, 103 participants were recruited from the Adult Health and Behavior (AHAB) Study, which investigates a variety of behavioral and biological traits among non-patient, middle-aged community volunteers. All participants were in good general health and free of the following: (1) medical diagnoses of cancer, stroke, diabetes requiring insulin treatment, chronic kidney or liver disease, or a lifetime history of psychotic symptoms; (2) use of psychotropic, glucocorticoid or cardiovascular (for example, antihypertensive or antiarrhythmic) medication; (3) conditions that affect cerebral blood flow and metabolism (for example, hypertension); and (4) any current DSM-IV (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition) axis I disorder as assessed by the non-patient version of the Structured Clinical Interview for DSM-IV.37 Written informed consent according to the guidelines of the University of Pittsburgh's Institutional Review Board was obtained from all participants upon their enrollment in the study. To minimize the risk of artifacts due to population stratification, we restricted analyses to Caucasian participants, after which both genotyping and functional magnetic resonance imaging data were available for 81 participants (43 women, mean age 44.70 ± 6.49 years).
