What defines a Controlled Substance?

A controlled substance is defined primarily by its potential for abuse and dependence. This classification is set forth by regulatory agencies, as certain substances can lead to addiction or misuse, posing a risk not only to individual users but also to the community. The emphasis on the potential for abuse is crucial, as it determines how the substance is scheduled within the legal framework, influencing the regulations surrounding its manufacture, distribution, and prescription.

While some drugs may have high medical benefits, as noted in another choice, this does not inherently categorize them as controlled substances; it's the risk of abuse that is the defining characteristic. Additionally, drugs that are considered to have no medical use are generally banned but are treated differently than those that can be legally prescribed under tight regulations. Drugs available over-the-counter lack the strict regulatory constraints of controlled substances mainly because they are considered safe for public use without a prescription. Thus, the essence of what defines a controlled substance lies in its misuse potential, which is precisely captured by the correct answer.