A counterfactual model was used to estimate the preventive effect of treatment for problem opioid use on opioid-related deaths in England between April 2008 and March 2011. [The counterfactual model is a method of evaluating impact, by considering what actually happened (the factual) and what would have happened in the absence of the intervention (the counterfactual).] It makes the assumption that: If X had not happened, then Y would have happened.

This was translated into the following question for the study: If no opioid misusing patients had been treated, how many would have died an opioid-related death?

Answering the question required data on the prevalence of opioid use in the general population, the extent of treatment provision, and the number of deaths related to opioid use.

Key points from summary and commentary
• A model was used to estimate the preventive effect of treatments for problem opioid use, based on data about the prevalence of opioid use in the general population, the extent of treatment provision, and the number of deaths related to opioid use.
• This revealed that there would have been 880 extra deaths per year in England between April 2008 and March 2011 if not for treatment.
• The analysis highlights “an important and underrecognized outcome” from the English substance use treatment system, and represents one of the largest studies of opioid deaths conducted to date