Participants were non-treatment seeking heavy drinkers recruited from the community through newspaper advertisements for study of naltrexone’s effects on drinking, urges, and mood in the natural environment (for details see Tidey et al., 2008). This study focuses on previously unreported data from the baseline period to avoid the complicating placebo and medication effects. Eligibility criteria included: 21 years of age, drinking at least 4 days per week, and reporting heavy drinking on at least 2 days per week on average over the preceding month (> 6 standard drinks for men, > 4 standard drinks for women; Flannery et al., 2002). Exclusionary criteria included abuse of, or dependence on, drugs other than nicotine and alcohol, current interest in or past treatment for alcohol problems, positive urine screen for opiates or cocaine (positive screens for marijuana were enrolled), positive pregnancy test, nursing, not using birth control (women), medications or medical conditions that counterindicated naltrexone treatment. A subset of participants provided consent for DNA collection and represents the current sample. As genotyping in this study began about 12 months after recruitment started, the
