Anticipatory response

An anticipatory response is the experience of a wide range of potential cognitive and physical effects that can occur immediately before the administration of a substance that the user is experienced with or addicted to. For example, benzodiazepine addicts will often find that their anxiety and nervousness is significantly reduced during the minutes preceding its ingestion, and many users who are addicted to intravenous heroin report that their body begins to subjectively slow down and relax in the moments prior to its injection. These changes typically feel as if they are a combination of both standard emotional responses to the current situation and more deeply rooted physiological changes that seem to arise from a form of unintentional Pavlovian conditioning.

Anticipatory response is most commonly induced under the influence of any substance that is sporadically or regularly taken over a long period of time, particularly when these substances become both familiar and addictive to their user.