Trends in the nonmedical use of prescription opioids (NMUPO) have been rising in the past few decades, causing increases in morbidity and mortality due to prescription opioids (POs). There is some evidence that NMUPO and PO dependence (POD) is correlated to the use of heroin, as well as some evidence that the rise in NMUPO may be linked to the increases in opioid prescribing seen in the past couple of decades. Despite increasing concerns, however, there has been no previous systematic review of the prevalence of POD.