I personally think there is more to it than that. I know a guy who from the moment he wakes up to the moment he goes to bed, he is stoned.
He owns his own successful businesses.
I know another guy on the other hand who does the same thing....
He owns a not so successful business and is constantly struggling.
Just because one partakes in cannabis (regardless of amount) doesnt always mean they are counterproductive. But yeah, a good portion of the time they can be.
I know I was when I was younger.