What physiological change occurs as a result of prolonged exposure to an abused substance?

Prolonged exposure to an abused substance leads to tolerance, which is a physiological change characterized by a decreased response to the drug over time. This occurs because the body adapts to the drug's presence, requiring higher doses to achieve the same effects that were initially experienced with lower amounts. Tolerance is a significant factor in substance abuse, as it can lead individuals to increase their consumption, which may enhance the risk of addiction and associated health issues.

The development of tolerance indicates that the body is altering its neurochemistry or receptor sensitivity in response to the continuous presence of the substance. This adjustment can impact various brain pathways involved in pleasure, reward, and metabolism. While craving, addiction, and euphoria are related concepts, they are not direct physiological changes resulting from the constant intake of a drug.