> Every single one of them denied impairment during those periods. Often vehemently so, belittling anyone who suggested they might be impaired as having succumbed to propaganda.

isn't that just common addiction response?

"no, nothing's wrong with me. my drugs aren't the problem - you are the problem"

I think most addicts when not high/drunk/fucked up off their substance of choice would admit that they they are more impaired and not good to drive when they are on their substance of choice.

But you'll still find some small percentage of them claiming they wouldn't be impaired.

Source: have actually spend a lot of time around addicts.