What is a drug defined as?

A drug is defined as a substance that changes the way the body or brain works. This definition encompasses both legal and illegal substances, including prescription medications, over-the-counter drugs, and illicit drugs, all of which can affect physical or mental functions.

Understanding this definition is important because it highlights that drugs are not limited to those substances that are illegal; many legal substances can also alter mood, perception, or physiological functions. The distinction is crucial for discussions around substance abuse, medication use, and public health, as it underscores the potential impact of both legal and illegal substances on an individual's health and behavior.

While mood alteration is a feature of many drugs, including some legal ones, the definition of a drug includes a broader scope than just mood changes, making the focus on how they work in the body and brain the most accurate definition.