Drug harmfulness is the degree to which a psychoactive drug is harmful to a user. Drug harmfulness is measured in various ways, such as by addictiveness and the potential for physical harm. More harmful drugs are called hard drugs and less harmful drugs are called soft drugs. The term hard drug is considered controversial by its critics because it implies that all the hard drugs cause severe harm.
The distinction between soft drugs and hard drugs is important in the drug policy of the Netherlands, where cannabis production, retailing and use come under official tolerance, subject to certain conditions. The Dutch Opium Law have two lists of drugs, List I and List II, that are colloquially considered to be lists of hard and soft drugs, respectively. Other countries typically have more than two categories. For example, the US has five schedules in the Controlled Substances Act, ranging from one through five. The UK has three classes in the Misuse of Drugs Act 1971: A, B and C.