Little Reefer Madness in this.

I think it's in writing somewhere that Welles had a pretty lax attitude towards weed. That being said, I think the way the characters react considering their background and the time period is appropriate (especially when that spas of a motel clerk flips out in true Reefer Madness style).

As the old saying goes- Nope

I thought of Reefer Madness too. But they were mainlining heroin too so it wasn't all misrepresentative or just Marijuana.

I think the Night Watchman's scream, when he sniffed the joint was intentionally over the top to poke a little fun at society's hysteric attitude towards Marijuana in the 1950's. Sort of an inside joke for those who have partaken of the good herb, that would slip past the Hays Code censors.