Medication data were obtained from GHC automated pharmacy files. These data have been shown to cover over 90% of the prescription medications used by GHC enrollees.(23 ) Total morphine equivalents dispensed were calculated for each opioid prescription filled during the follow-up period, defined by the quantity of pills dispensed multiplied by their strength (in milligrams (mg)), multiplied by a conversion factor.(22 (link)) The average daily morphine equivalent dose dispensed was then calculated for 90 day exposure windows (see Analysis section) by summing the morphine equivalents for the prescriptions dispensed for the 90-day period and dividing by 90. For each 90 day exposure window and person, the average daily opioid dose dispensed was calculated and categorized into none, 1 to 19 mg, 20 to 49 mg, 50 to 99 mg and 100 mg or more.