An Iowa paper reports that the leading cause of arrests in the county immediately south of Des Moines is drugs. They identify drugs or alcohol as the reason for 22 of 29 arrests in the county.
Statutory definitions can be very specific or vague, depending on the whim of the legislature. Of course, they cannot be too vague, as that can lead to their being found unconstitutional because of that vagueness. For a law to be meaningfully applied to a person, they should have some possibility of understanding that it applies to them.