Opioid dependence (OD) is a serious, prevalent disorder and the number of people using opioids in the United States has been increasing since 1990 (Anthony et al., 1994; Regier et al., 1990; Substance Abuse and Mental Health Services Administration, 2007). In 2006, 0.8% of Americans aged 12 or older met criteria for a lifetime opioid use disorder and 0.4% were treated for an opioid-related problem in the past year (Substance Abuse and Mental Health Services Administration, 2007).
