, Volume 115, Issue 1–2, pp 1–8 | Cite as

Discriminative stimulus and subjective effects of theobromine and caffeine in humans

  • Geoffrey K. Mumford
  • Suzette M. Evans
  • Barbara J. Kaminski
  • Kenzie L. Preston
  • Christine A. Sannerud
  • Kenneth Silverman
  • Roland R. Griffiths
Original Investigations


Theobromine versus placebo discrimination and caffeine versus placebo discrimination were studied in two consecutive experiments in seven volunteers who abstained from methylxanthines. Daily sessions involved PO double-blind ingestion of two sets of capsules sequentially, one of which contained drug and the other placebo. Subjects attempted to identify, and were later informed, which set of capsules contained the drug. In each experiment subjects were exposed to progressively lower doses. Five subjects acquired the theobromine discrimination; the lowest dose discriminated ranged from 100 to 560 mg. All seven subjects acquired the caffeine discrimination; the lowest dose discriminated ranged from 1.8 to 178 mg. A final experiment evaluated subjective effect ratings following 560 mg theobromine, 178 mg caffeine and placebo, which were administered double-blind in capsules once daily, five times each in mixed sequence. Caffeine produced changes in both group and individual ratings (e.g. increased well-being, energy, social disposition and alert). Theobromine did not produce changes in group ratings but changed ratings in some subjects. Across subjects, sensitivity to caffeine discriminative effects in the discrimination experiment correlated significantly with the number and magnitude of caffeine subjective effects in the final experiment. This study documents modest discriminative effects of theobromine in humans, but the basis of the discrimination is unclear. This study suggests that commonly consumed cocoa products contain behaviorally active doses of caffeine and possibly theobromine.

Key words

Theobromine Caffeine Methylxanthine Cocoa Chocolate Drug discrimination Subjective effects Humans 


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Copyright information

© Springer-Verlag 1994

Authors and Affiliations

  • Geoffrey K. Mumford
    • 1
  • Suzette M. Evans
    • 2
  • Barbara J. Kaminski
    • 1
  • Kenzie L. Preston
    • 1
    • 3
  • Christine A. Sannerud
    • 1
    • 4
  • Kenneth Silverman
    • 1
    • 3
  • Roland R. Griffiths
    • 1
    • 5
  1. 1.Department of Psychiatry and Behavioral SciencesJohns Hopkins University School of Medicine, Behavioral Biology Research CenterBaltimoreUSA
  2. 2.Clinical Pharmacology Branch, National Institute on Drug Abuse, Addiction Research CenterBaltimoreUSA
  3. 3.Treatment Branch, National Institute on Drug Abuse, Addiction Research CenterBaltimoreUSA
  4. 4.Preclinical Pharmacology Laboratory, National Institute on Drug AbuseAddiction Research CenterBaltimoreUSA
  5. 5.Department of NeuroscienceJohn Hopkins University School of Medicine, Behavioral Biology Research CenterBaltimoreUSA

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