You are correct in that it is utter B.S., but note the careful wording:
"marijuana as a factor"
Meaning...well...not much of anything other than more people come into the emergency room having smoked marijuana than having taken heroin, which is what any informed person would expect, given that a lot more people smoke marijuana than take heroin.
Note: that doesn't mean that the marijuana use is why they're in the emergency room.
It's kinda like those "alcohol-related traffic fatalities" that we hear a lot about. Contrary to popular belief, they aren't necessarily fatalities caused by alcohol; they're just a method of inflating the stats to make them more interesting or alarming.
It's fun and profitable to lie^H^H^Hmislead with statistics.