Which schedule of controlled substances has the highest potential for abuse?

Schedule I controlled substances are classified as having the highest potential for abuse, according to federal law. This schedule includes substances that have no accepted medical use in the United States and a high potential for addiction and dependency. Examples of Schedule I drugs include heroin, lysergic acid diethylamide (LSD), and marijuana (at the federal level). Because these substances are considered extremely dangerous and lack any legitimate therapeutic use in the view of the federal government, they are restricted to research settings with strict regulations.

In contrast, the other schedules (II, III, and IV) contain substances that have recognized medical uses but vary in their potential for abuse. Schedule II drugs, such as opioids and certain stimulants, are also considered to have a high potential for abuse but can be prescribed and dispensed under stringent regulations. Schedules III and IV include substances with progressively lower potential for abuse and greater accepted medical use, thus categorizing them as having less risk compared to Schedule I drugs.