Expectation for stimulant type modifies caffeine's effects on mood and cognition among college students.

Caffeine is regularly used by college students to enhance mood and academic performance. Although high doses confer risk for negative consequences, moderate doses of caffeine may lead to acute improvements in mood and cognitive functioning. Notably, the pharmacological effects of caffeine may be enhanced by expectancy effects. College students may also engage in nonmedical prescription stimulant use for similar purposes, as students expect strong cognitive enhancement from prescription stimulants and consider them to be more efficacious than caffeine. The purpose of the current study was to examine whether the pharmacological effects of caffeine on mood/drug effects and cognitive performance are enhanced when expecting a conceivably stronger stimulant (i.e., Adderall) compared to when expecting caffeine. Sixty-five undergraduate students were randomized to condition across two variables: drug ingested (placebo or 200 mg caffeine) and drug expected (caffeine or Adderall). Participants completed self-report measures of mood and drug effects pre- and post-drug, as well as cognitive assessments post-drug. There were significant main effects of drug ingested and drug expected on several post-drug measures. Subjects receiving caffeine reported feeling more high, stimulated, anxious, and motivated than subjects receiving placebo. Further, subjects expecting Adderall reported stronger amphetamine effects and feeling more high, and performed better on a working memory test, than those expecting caffeine. Effects tended to be strongest in participants receiving caffeine and expecting Adderall. Modifying expectancies, in conjunction with the pharmacological properties of caffeine at moderate doses, may be one mechanism by which college students may experience differential effects of caffeine. (PsycInfo Database Record (c) 2022 APA, all rights reserved).