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

Schedule I controlled substances are classified as having the highest potential for abuse and have no accepted medical use in the United States. Drugs within this schedule can lead to severe psychological or physical dependence. Examples of Schedule I substances include heroin, LSD, and cannabis (marijuana) in certain jurisdictions.

The classification in Schedule I reflects the government's assessment of danger associated with these substances, including their potential to be misused. Unlike substances in lower schedules, which can have accepted medical uses and are subject to varying levels of restriction, Schedule I substances are completely prohibited for medical use under federal law, making them the most tightly controlled.

In contrast, substances listed in lower schedules (like II, III, and IV) can have accepted medical uses and show varying degrees of potential for abuse, but none match the classification and restrictions of Schedule I substances.