Can differences in the type, nature or amount of polysubstance use explain the increased risk of non-fatal overdose among psychologically distressed people who inject drugs?

The types of polysubstance use profiles did not differ between people who inject drugs with and without severe psychological distress. However, the nature of use of one particular polysubstance profile placed the former group at a strongly increased risk of non-fatal overdose, while the nature of polysubstance use involving opioid substitution therapies was protective only among the latter group. The findings identify polysubstance use profiles of importance to drug-related harms among individuals with psychological problems.