Dear Patrick, please find attached file for the questionnaire used in our study noting that we have studied the relationship between cannabis use and severity of injury through counting days away from work and ISS (injury severity SCORE). Also, you can add to this research idea by studying sleep profile of injured workers or relation with substance abuse.
Here is a link to a survey that I have used for similar work on Non-Fatal Occupational Injuries and Safety Climate. This was developed by the Marlin Company and the American Institute of Stress.