As a value judgment
Philip Jenkins points out that there are two issues with the term “drug abuse”. First, that constitutes a “drug” is debatable. For instance, GHB, a naturally occurring substance in the central nervous system is considered a drug, and is illegal in many countries, while nicotine is not officially considered a drug in most countries. Second, the word “abuse” implies a recognized standard of use for any substance. Drinking an occasional glass of wine is considered acceptable in many Western countries, while drinking several bottles is seen as an abuse. Strict temperance advocates, which may or may not be religiously motivated, would see drinking even one glass as an abuse, and some groups even condemn caffeine use in any quantity. Similarly, adopting the view that any (recreational) use of marijuana or amphetamines constitutes drug abuse implies that we have already decided that substance is harmful even in minute quantities.