Epidemiology Canada now has the second highest number of opioid prescriptions per capita in the world. The rate of prescriptions has increased over the last decade, most notably in adults over 55 years of age. A recognition of the importance of treating pain has influenced this increase, but higher rates of opioid prescribing have produced undesirable outcomes including the misuse of medication as well as an increased number of deaths and emergency department visits attributable to opioids. Diverse psychiatric disorders, such as major depression, now also occur in 40% of those with an opioid use disorder (OUD). Neuroscience We now understand that addictive behaviors are caused by both environmental and genetic factors. Although OUD has historically been perceived as a weakness of character, it is now clear that it is a chronic disease, which results from a complex interaction between a substance, such as opioid, environmental factors, and an individual's genotype. Unfortunately, this evidence has yet to be successfully translated into clinical practice and most physicians are unable to diagnose and manage OUD patients appropriately.Clinical guidelines Many clinical guidelines for the management of chronic, non-cancer pain are available. All guidelines identify the need to assess the patient appropriately and screen for factors associated with misuse before prescribing opioids. Guidelines generally acknowledge that patients should not be denied appropriate pain management, but that some patients will require close supervision and frequent follow-up to prevent the misuse of prescription opioids.