certain recreational drugs also have uses as a therapeutic drug. heroin can be used as an analgesic (a painkiller) and methamphetamine is used to treat narcolepsy or adhd. recreational drugs can be dangerous, certain countries have made it illegal to have or take them outside a medical context. most of the time, this is because they can be addictive or that they are very dangerous when combined with other drugs. that way, cannabis-based products are legal in the netherlands, but illegal in many other countries.