I definitely would like to add education to that study, but it can't be the only factor. But drug abuse is higher in the US than in any other country. In fact in the US, deaths from drug abuse are nearly 3x higher than the next highest country. That's why we need a comprehensive (preferably worldwide) study. Unfortunately, people only want to fund studies that push their bias.
You’re stretching common sense but I don’t discount tertiary factors. But there is a direct connection between gun deaths and gun availability.