title: Caffeine withdrawal, acute effects, tolerance, and absence of net beneficial effects of chronic administration: cerebral blood flow velocity, quantitative EEG, and subjective effects.
abstract: BACKGROUND
  Although the subjective effects of caffeine abstinence, acute and chronic administration, and tolerance are well described, the corresponding neurophysiological effects are not.
  
  
  OBJECTIVE
  Caffeine withdrawal, acute caffeine effects, caffeine tolerance, and net beneficial effects of chronic caffeine administration were investigated using cerebral blood flow velocity, quantitative electroencephalography (EEG), and subjective effects.
  
  
  METHODS
  Sixteen regular caffeine users participated in this double-blind, within-subject study during which they received acute caffeine and placebo challenges (1) while maintained on 400 mg caffeine daily for > or =14 days and (2) while maintained on placebo for > or =14 days. Blood flow velocity was determined for the middle (MCA) and anterior (ACA) cerebral arteries using pulsed transcranial Doppler sonography. EEG was recorded from 16 scalp sites. Subjective effects were assessed with questionnaires.
  
  
  RESULTS
  Acute caffeine abstinence (evaluated 24 h after placebo substitution) increased mean, systolic, and diastolic velocity in the MCA and ACA and decreased pulsatility index in the MCA. Acute caffeine abstinence increased EEG theta and decreased beta 2 power. Acute caffeine abstinence also increased measures of Tired, Fatigue, Sluggish, and Weary and decreased ratings of Energetic, Friendly, Lively, and Vigor. Acute caffeine effects were demonstrated across a wide range of measures, including cerebral blood flow, EEG, and subjective effects. Tolerance and "complete" tolerance were observed on subjective but not physiological measures. Chronic caffeine effects were demonstrated only on the measure of EEG beta 2 power.
  
  
  CONCLUSIONS
  Acute caffeine abstinence and administration produced changes in cerebral blood flow velocity, EEG, and subjective effects. Tolerance to subjective but not physiological measures was demonstrated. There was almost no evidence for net effects of chronic caffeine administration on these measures. Overall, these findings provide the most rigorous demonstration to date of physiological effects of caffeine withdrawal.
authors.affiliation: Department of Psychiatry, University of Vermont College of Medicine, SATC-UHC, Room 1415, Burlington, VT, 05401, USA. stacey.sigmon@uvm.edu
authors.forename: Stacey C
authors.initials: SC
authors.lastname: Sigmon
authors.forename: Ronald I
authors.initials: RI
authors.lastname: Herning
authors.forename: Warren
authors.initials: W
authors.lastname: Better
authors.forename: Jean L
authors.initials: JL
authors.lastname: Cadet
authors.forename: Roland R
authors.initials: RR
authors.lastname: Griffiths
mesh_terms: D000328:Adult; D020771:Anterior Cerebral Artery / Q000187:drug effects / Q000378:metabolism; D002110:Caffeine / Q000008:administration & dosage* / Q000009:adverse effects; D000697:Central Nervous System Stimulants / Q000008:administration & dosage* / Q000009:adverse effects; D002560:Cerebrovascular Circulation / Q000187:drug effects*; D018592:Cross-Over Studies; D004311:Double-Blind Method; D004361:Drug Tolerance; D004569:Electroencephalography; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020768:Middle Cerebral Artery / Q000187:drug effects / Q000378:metabolism; D013375:Substance Withdrawal Syndrome / Q000503:physiopathology* / Q000523:psychology; D011795:Surveys and Questionnaires; D017585:Ultrasonography, Doppler, Transcranial; D055815:Young Adult
chemical_list: D000697:Central Nervous System Stimulants; D002110:Caffeine