A critical review of caffeine withdrawal: empirical validation of symptoms and signs, incidence, severity, and associated features

Caffeine in the treatment of pain

BACKGROUND AND OBJECTIVES

Caffeine is a widely used substance with effects on several systems, presenting characteristic of pharmacokinetic and pharmacodynamic which cause interactions with several drugs. This study's objective is to review the effects caused by caffeine.

CONTENT

This review assesses the caffeine pharmacology, its action mechanisms, indications, contraindications, doses, interactions and adverse effects.

CONCLUSIONS

There are insufficient double-blind randomized controlled studies that assess the analgesic effect of caffeine on several painful syndromes. Patients presenting chronic pain need caution when it comes to tolerance development, abstinence and drug interaction from chronic caffeine use.

Genome-wide association analysis of coffee drinking suggests association with CYP1A1/CYP1A2 and NRCAM

Coffee consumption is a model for addictive behavior. We performed a meta-analysis of genome-wide association studies (GWASs) on coffee intake from 8 Caucasian cohorts (N=18 176) and sought replication of our top findings in a further 7929 individuals. We also performed a gene expression analysis treating different cell lines with caffeine. Genome-wide significant association was observed for two single-nucleotide polymorphisms (SNPs) in the 15q24 region. The two SNPs rs2470893 and rs2472297 (P-values=1.6 × 10(-11) and 2.7 × 10(-11)), which were also in strong linkage disequilibrium (r(2)=0.7) with each other, lie in the 23-kb long commonly shared 5' flanking region between CYP1A1 and CYP1A2 genes. CYP1A1 was found to be downregulated in lymphoblastoid cell lines treated with caffeine. CYP1A1 is known to metabolize polycyclic aromatic hydrocarbons, which are important constituents of coffee, whereas CYP1A2 is involved in the primary metabolism of caffeine. Significant evidence of association was also detected at rs382140 (P-value=3.9 × 10(-09)) near NRCAM-a gene implicated in vulnerability to addiction, and at another independent hit rs6495122 (P-value=7.1 × 10(-09))-an SNP associated with blood pressure-in the 15q24 region near the gene ULK3, in the meta-analysis of discovery and replication cohorts. Our results from GWASs and expression analysis also strongly implicate CAB39L in coffee drinking. Pathway analysis of differentially expressed genes revealed significantly enriched ubiquitin proteasome (P-value=2.2 × 10(-05)) and Parkinson's disease pathways (P-value=3.6 × 10(-05)).

Recognition and management of excessive sleepiness in the primary care setting

BACKGROUND

Excessive sleepiness often goes unrecognized in the primary care setting despite its high prevalence and deleterious effects on both individual and public safety. Patients with neurologic and psychiatric illnesses, as well as those with acute and chronic medical conditions, plus those with sleep disorders, often have symptoms of excessive sleepiness, tiredness, and fatigue. Recognition and prompt treatment of these symptoms are important, even though their etiology may not be immediately understood. This review focuses on the underlying causes, consequences, identification, and treatment of excessive sleepiness.

DATA SOURCES

A search of the literature to 2007 was performed using the PubMed search engine. English-language articles were identified using the following search terms: excessive sleepiness, fatigue, circadian rhythm, obstructive sleep apnea, shift work disorder, narcolepsy, drowsy driving, and wakefulness. Additional references were identified through bibliography reviews of relevant articles.

DATA SYNTHESIS

Current assessments of the prevalence, consequences, and etiologies of excessive sleepiness, with leading treatment strategies, were extracted, reviewed, and summarized to meet the objectives of this article.

CONCLUSIONS

Excessive sleepiness is associated with a wide range of medical, neurologic, and psychiatric disorders frequently seen in primary care practice. Excessive sleepiness is a serious, debilitating, potentially life-threatening condition, yet also treatable, and it is important to initiate appropriate intervention as early as possible. Physicians should place increasing emphasis on the substantial benefits that accompany improvements in wakefulness.

Development of the caffeine withdrawal symptom questionnaire: caffeine withdrawal symptoms cluster into 7 factors

BACKGROUND

Habitual caffeine consumers who abstain from caffeine experience withdrawal symptoms such as headache, fatigue, difficulty concentrating, mood disturbances, and flu-like symptoms (Juliano and Griffiths, 2004). The caffeine withdrawal syndrome has been documented across many experimental studies; however, little is known about how withdrawal symptoms co-vary during a discrete episode. Furthermore, a validated measure of caffeine withdrawal is lacking.

OBJECTIVE

To develop, evaluate, and reduce a 23-item measure of caffeine withdrawal symptoms; the Caffeine Withdrawal Symptom Questionnaire (CWSQ), to a set of composite variables.

METHODS

Caffeine consumers (N=213) completed the CWSQ after 16h of caffeine abstinence. A subset of participants also completed the CWSQ during a preceding baseline period and/or after double-blind consumption of caffeinated coffee.

RESULTS

Principal components analysis resulted in a solution comprised of 7-factors: (1) Fatigue/drowsiness; (2) Low alertness/difficulty concentrating; (3) Mood disturbances; (4) Low sociability/motivation to work; (5) Nausea/upset stomach; (6) Flu-like feelings; and (7) Headache. With the exception of nausea/upset stomach, the CWSQ total score and individual composite scores were significantly greater during caffeine abstinence relative to both baseline and double-blind consumption of caffeinated coffee, thereby demonstrating sensitivity of the measure. Compared to non-daily coffee consumers, daily consumers had greater increases in total withdrawal, fatigue/drowsiness, low alertness/difficulty concentrating, mood disturbances, and headache.

CONCLUSIONS

Future directions include replication, assessment on a clinical population, and further examination of psychometric properties of the CWSQ. The CWSQ should facilitate the assessment and diagnosis of caffeine withdrawal and increase our knowledge of the caffeine withdrawal syndrome.

Prevalence and determinants of headaches in Hawaii: the Hilo Women's Health Study

BACKGROUND

Headache frequency has been associated with ethnicity, menopause, abdominal obesity and stress.

AIM

To examine the prevalence and determinants of headaches in the multi-ethnic community of Hilo, Hawaii.

SUBJECTS AND METHODS

A random sample of 1824 women aged 16-100 was recruited by postal survey; 206 women aged 45-55 were recruited for clinical measures. Both studies queried the presence/absence of headaches during the past 2 weeks. The clinical study also examined migraines and tension headaches. Headaches were examined in relation to demographic, reproductive and lifestyle variables, stress, symptoms and anthropometric measures.

RESULTS

Headache prevalence was 47%. Japanese women were less likely to report headaches compared to women of European descent, but, after controlling for measures of stress, Japanese women were at a higher risk for headaches. Post-menopausal women were half as likely to report headaches compared with pre-menopausal women. Women with children younger than 18 were 4-times as likely to report migraines compared with women who did not have children younger than 18.

CONCLUSION

Standardized measures of daily hassles, life and job satisfaction were not associated with headaches. The relationship between headaches and having young children suggests that the everyday stress of family life is a headache risk. This may be particularly true in Hilo, Hawaii, where the value of family is culturally prioritized.

Caffeine as an analgesic adjuvant for acute pain in adults

BACKGROUND

Caffeine has been added to common analgesics such as paracetamol, ibuprofen, and aspirin, in the belief that it enhances analgesic efficacy. Evidence to support this belief is limited and often based on invalid comparisons.

OBJECTIVES

To assess the relative efficacy in acute pain of a single dose of any analgesic plus caffeine against the same dose of analgesic alone.

SEARCH METHODS

We searched CENTRAL, MEDLINE, EMBASE, and the Oxford Pain Relief Database to January 2012, and also carried out Internet searches and contacted pharmaceutical companies known to have carried out trials that have not been published.

SELECTION CRITERIA

We included randomised, double-blind studies that compared a single dose of analgesic plus caffeine with the same dose of the analgesic alone in the treatment of acute pain.

DATA COLLECTION AND ANALYSIS

Two review authors independently assessed eligibility and quality of studies, and extracted data. Any disagreements or uncertainties were settled by discussion with a third review author. We sought any validated measure of analgesic efficacy, but particularly the number of participants experiencing at least 50% of the maximum possible pain relief over four to six hours, participants reporting a global evaluation of treatment of very good or excellent, or headache relief after two hours. We pooled comparable data to look for a statistically significant difference, and calculated numbers needed to treat to benefit (NNT) with caffeine. We also looked for any numerical superiority associated with the addition of caffeine, and information about any serious adverse events.

MAIN RESULTS

We identified 19 studies (7238 participants) in valid comparisons. Most studies used paracetamol or ibuprofen, with 100 mg to 130 mg caffeine, and the most common pain conditions studied were postoperative dental pain, postpartum pain, and headache. There was a small but statistically significant benefit with caffeine used at doses of 100 mg or more, which was not dependent on the pain condition or type of analgesic. About 5% to 10% more participants achieve a good level of pain relief (at least 50% of the maximum) with the addition of caffeine, giving a NNT of about 15.Most comparisons individually demonstrated numerical superiority with caffeine, but not statistical superiority. One serious adverse event was reported with caffeine, but was considered unrelated to any study medication.We know or suspect of the existence of 20 additional studies with 9785 participants for which data for analysis were not obtainable. The additional analgesic effect of caffeine remained statistically significant but clinically less important even if all the known missing data had no effect; that is not likely to be the case.

AUTHORS' CONCLUSIONS

The addition of caffeine (≥ 100 mg) to a standard dose of commonly used analgesics provides a small but important increase in the proportion of participants who experience a good level of pain relief.

The Effects of Dietary Caffeine Use and Abstention on Blood Oxygen Level-Dependent Activation and Cerebral Blood Flow

BACKGROUND

Caffeine is a known vasoconstrictor that reduces resting cerebral blood flow (CBF) throughout the brain. This effect may be problematic in functional magnetic resonance imaging (fMRI) research, as the blood oxygen level-dependent (BOLD) signal is a complex interaction of CBF and other factors that are dependent on changes in neural activity. It is unknown whether changes in the BOLD signal during an fMRI experiment could be affected by subjects' recent use or abstinence from dietary caffeine.

METHODS

Here, we report two similar studies (n=45 and 17) that measure the effects of caffeine on BOLD activation, BOLD time course parameters, and CBF. Using a factorial design, low, moderate, and high caffeine consumers received either caffeine (250 mg) or placebo during normal caffeine use (satiated state) or after 30 hours of abstention (abstinent state). The fMRI of a reaction time task and resting-state CBF were collected.

RESULTS

In general, acute caffeine administration reduced the time to peak and full width at half maximum of the BOLD time course, and CBF across both studies. Caffeine also produced a small reduction in BOLD activation. The majority of these reductions across measures were moderated by neither the level of caffeine use, nor the abstinent or satiated state.

CONCLUSIONS

These results suggest that dietary caffeine use does not produce a significant effect on task-related BOLD activation.

Characterization of individuals seeking treatment for caffeine dependence

Previous investigations have identified individuals who meet criteria for Diagnostic and Statistical Manual of Mental Disorders (4th ed., text rev.; DSM-IV-TR; American Psychiatric Association, 2000) substance dependence as applied to caffeine, but there is little research on treatments for caffeine dependence. This study aimed to thoroughly characterize individuals who are seeking treatment for problematic caffeine use. Ninety-four individuals who identified as being psychologically or physically dependent on caffeine, or who had tried unsuccessfully to modify caffeine consumption participated in a face-to-face diagnostic clinical interview. They also completed measures concerning caffeine use and quitting history, reasons for seeking treatment, and standardized self-report measures of psychological functioning. Caffeine treatment seekers (mean age 41 years, 55% women) consumed an average of 548 mg caffeine per day. The primary source of caffeine was coffee for 50% of the sample and soft drinks for 37%. Eighty-eight percent reported prior serious attempts to modify caffeine use (mean 2.7 prior attempts), and 43% reported being advised by a medical professional to reduce or eliminate caffeine. Ninety-three percent met criteria for caffeine dependence when generic DSM-IV-TR substance dependence criteria were applied to caffeine use. The most commonly endorsed criteria were withdrawal (96%), persistent desire or unsuccessful efforts to control use (89%), and use despite knowledge of physical or psychological problems caused by caffeine (87%). The most common reasons for wanting to modify caffeine use were health-related (59%) and not wanting to be dependent on caffeine (35%). This investigation reveals that there are individuals with problematic caffeine use who are seeking treatment and suggests that there is a need for effective caffeine dependence treatments.

Evaluating Dependence Criteria for Caffeine

Background: Although caffeine is the most widely used mood-altering drug in the world, few studies have operationalized and characterized Diagnostic and Statistical Manual IV (DSM-IV) substance dependence criteria applied to caffeine. Methods: As a part of a nosological study of substance use disorders funded by the National Institute on Drug Abuse, we assessed caffeine use and dependence symptoms among high school and college students, drug treatment patients, and pain clinic patients who reported caffeine use in the last 7 days and also reported use of alcohol, nicotine, or illicit drugs within the past year (n=167). Results: Thirty-five percent met the criteria for dependence when all seven of the adopted DSM dependence criteria were used. Rates of endorsement of several of the most applicable diagnostic criteria were as follows: 26% withdrawal, 23% desire to cut down or control use, and 44% continued use despite harm. In addition, 34% endorsed craving, 26% said they needed caffeine to function, and 10% indicated that they talked to a physician or counselor about problems experienced with caffeine. There was a trend towards increased caffeine dependence among those dependent on nicotine or alcohol. Within a subgroup that had used caffeine, alcohol, and nicotine in the past year, 28% fulfilled criteria for caffeine dependence compared to 50% for alcohol and 80% for nicotine. Conclusion: The present study adds to a growing literature suggesting the reliability, validity, and clinical utility of the caffeine dependence diagnosis. Recognition of caffeine dependence in the DSM-V may be clinically useful.

Advanced policy options to regulate sugar-sweetened beverages to support public health

Consumption of sugar-sweetened beverages (SSBs) has increased worldwide. As public health studies expose the detrimental impact of SSBs, consumer protection and public health advocates have called for increased government control. A major focus has been on restricting marketing of SSBs to children, but many innovative policy options--legally defensible ways to regulate SSBs and support public health--are largely unexplored. We describe the public health, economic, and retail marketing research related to SSBs (including energy drinks). We review policy options available to governments, including mandatory factual disclosures, earmarked taxation, and regulating sales, including placement within retail and food service establishments, and schools. Our review describes recent international initiatives and classifies options available in the United States by jurisdiction (federal, state, and local) based on legal viability.

Nicotine withdrawal exacerbates fear reactivity to CO₂-induced bodily sensations among smokers

INTRODUCTION

Independent lines of research suggest that smoking increases the prospective risk of panic disorder. Studies that have examined the hypothesized link between nicotine withdrawal and panic have typically employed light smokers or lacked optimal control groups. Our laboratory team previously found, for example, that smokers who abstained from cigarettes for 12 hr demonstrated greater fear reactivity to a CO(2) rebreathing challenge than nonsmokers. However, the absence of a smoking-as-usual group limited our ability to draw conclusions about the potential role of nicotine withdrawal.

METHODS

We exposed 27 heavy smokers who abstained from smoking for 12 hr and 27 heavy smokers who smoked as usual to a 5-min CO(2) rebreathing challenge.

RESULTS

More intense prechallenge nicotine withdrawal symptoms (regardless of group status) were associated with more severe panicky symptoms and a stronger urge to escape during the challenge, even after we controlled for prechallenge anxiety and daily cigarette use. Unexpectedly, group status did not predict challenge reactivity.

CONCLUSION

Smokers who regularly experience intense withdrawal symptoms, regardless of length of smoking abstinence, may be at heightened risk for experiencing panic attacks.

Sports drinks and energy drinks for children and adolescents: are they appropriate?

Sports and energy drinks are being marketed to children and adolescents for a wide variety of inappropriate uses. Sports drinks and energy drinks are significantly different products, and the terms should not be used interchangeably. The primary objectives of this clinical report are to define the ingredients of sports and energy drinks, categorize the similarities and differences between the products, and discuss misuses and abuses. Secondary objectives are to encourage screening during annual physical examinations for sports and energy drink use, to understand the reasons why youth consumption is widespread, and to improve education aimed at decreasing or eliminating the inappropriate use of these beverages by children and adolescents. Rigorous review and analysis of the literature reveal that caffeine and other stimulant substances contained in energy drinks have no place in the diet of children and adolescents. Furthermore, frequent or excessive intake of caloric sports drinks can substantially increase the risk for overweight or obesity in children and adolescents. Discussion regarding the appropriate use of sports drinks in the youth athlete who participates regularly in endurance or high-intensity sports and vigorous physical activity is beyond the scope of this report.

Methylxanthines and human health: epidemiological and experimental evidence

When considering methylxanthines and human health, it must be recognized that in many countries most caffeine is consumed as coffee. This is further confounded by the fact that coffee contains many bioactive substances in addition to caffeine; it is rich in phenols (quinides, chlorogenic acid, and lactones) and also has diterpenes (fatty acid esters), potassium, niacin, magnesium, and the vitamin B(3) precursor trigonelline. There is a paradox as consumption of either caffeine or caffeinated coffee results in a marked insulin resistance and yet habitual coffee consumption has repeatedly been reported to markedly reduce the risk for type 2 diabetes. There is strong evidence that caffeine reduces insulin sensitivity in skeletal muscle and this may be due to a combination of direct antagonism of A(1) receptors and indirectly β-adrenergic stimulation as a result of increased sympathetic activity. Caffeine may also induce reduced hepatic glucose output. With the exception of bone mineral, there is little evidence that caffeine impacts negatively on other health issues. Coffee does not increase the risk of cardiovascular diseases or cancers and there is some evidence suggesting a positive relationship for the former and for some cancers, particularly hepatic cancer.

Effects of caffeine on sleep and cognition

Caffeine can be used effectively to manipulate our mental state. It is beneficial in restoring low levels of wakefulness and in counteracting degraded cognitive task performance due to sleep deprivation. However, caffeine may produce detrimental effects on subsequent sleep, resulting in daytime sleepiness. This justifies a careful consideration of risks related to sleep deprivation in combination with caffeine consumption, especially in adolescents. The efficacy of caffeine to restore detrimental effects of sleep deprivation seems to be partly due to caffeine expectancy and to placebo effects. The claim that stimulant effects of caffeine are related to withdrawal or withdrawal reversal seems to be untenable.

Methylxanthines and sleep

Caffeine is widely used to promote wakefulness and counteract fatigue induced by restriction of sleep, but also to counteract the effects of caffeine abstinence. Adenosine is a physiological molecule, which in the central nervous system acts predominantly as an inhibitory neuromodulator. Adenosine is also a sleep-promoting molecule. Caffeine binds to adenosine receptors, and the antagonism of the adenosinergic system is believed to be the mechanism through which caffeine counteracts sleep in humans as well as in other species. The sensitivity for caffeine varies markedly among individuals. Recently, genetic variations in genes related to adenosine metabolism have provided at least a partial explanation for this variability. The main effects of caffeine on sleep are decreased sleep latency, shortened total sleep time, decrease in power in the delta range, and sleep fragmentation. Caffeine may also decrease the accumulation of sleep propensity during waking, thus inducing long-term harmful effects on sleep quality.

Adenosine receptors and brain diseases: neuroprotection and neurodegeneration

Adenosine acts in parallel as a neuromodulator and as a homeostatic modulator in the central nervous system. Its neuromodulatory role relies on a balanced activation of inhibitory A(1) receptors (A1R) and facilitatory A(2A) receptors (A2AR), mostly controlling excitatory glutamatergic synapses: A1R impose a tonic brake on excitatory transmission, whereas A2AR are selectively engaged to promote synaptic plasticity phenomena. This neuromodulatory role of adenosine is strikingly similar to the role of adenosine in the control of brain disorders; thus, A1R mostly act as a hurdle that needs to be overcame to begin neurodegeneration and, accordingly, A1R only effectively control neurodegeneration if activated in the temporal vicinity of brain insults; in contrast, the blockade of A2AR alleviates the long-term burden of brain disorders in different neurodegenerative conditions such as ischemia, epilepsy, Parkinson's or Alzheimer's disease and also seem to afford benefits in some psychiatric conditions. In spite of this qualitative agreement between neuromodulation and neuroprotection by A1R and A2AR, it is still unclear if the role of A1R and A2AR in the control of neuroprotection is mostly due to the control of glutamatergic transmission, or if it is instead due to the different homeostatic roles of these receptors related with the control of metabolism, of neuron-glia communication, of neuroinflammation, of neurogenesis or of the control of action of growth factors. In spite of this current mechanistic uncertainty, it seems evident that targeting adenosine receptors might indeed constitute a novel strategy to control the demise of different neurological and psychiatric disorders.

Interaction between drug and placebo effects: a cross-over balanced placebo design trial

Background

The total effect of a medication is the sum of its drug effect, placebo effect (meaning response), and their possible interaction. Current interpretation of clinical trials' results assumes no interaction. Demonstrating such an interaction has been difficult due to lack of an appropriate study design.

Methods

180 adults were randomized to caffeine (300 mg) or placebo groups. Each group received the assigned intervention described by the investigators as caffeine or placebo, in a randomized crossover design. 4-hour-area-under-the-curve of energy, sleepiness, nausea (on 100 mm visual analog scales), and systolic blood pressure levels as well as caffeine pharmacokinetics (in 22 volunteers nested in the caffeine group) were determined. Caffeine drug, placebo, placebo-plus-interaction, and total effects were estimated by comparing outcomes after, receiving caffeine described as placebo to receiving placebo described as placebo, receiving placebo described as caffeine or placebo, receiving caffeine described as caffeine or placebo, and receiving caffeine described as caffeine to receiving placebo described as placebo, respectively.

Results

The placebo effect on area-under-the-curve of energy (mean difference) and sleepiness (geometric mean ratio) was larger than placebo-plus-interaction effect (16.6 [95% CI, 4.1 to 29.0] vs. 8.4 [-4.2 to 21.0] mm*hr and 0.58 [0.39 to 0.86] vs. 0.69 [0.49 to 0.97], respectively), similar in size to drug effect (20.8 [3.8 to 37.8] mm*hr and 0.49 [0.30 to 0.91], respectively), and its combination with the later was larger than total caffeine effect (29.5 [11.9 to 47.1] mm*hr and 0.37 [0.22 to 0.64]). Placebo-plus-interaction effect increased caffeine terminal half-life by 0.40 [0.12 to 0.68] hr (P = 0.007).

Conclusions

Drug and placebo effects of a medication may be less than additive, which influences the interpretation of clinical trials. The placebo effect may increase active drug terminal half-life, a novel mechanism of placebo action.

Trial Registration

ClinicalTrials.gov identification number - NCT00426010.

Adolescent substance use, sleep, and academic achievement: evidence of harm due to caffeine

Using academic achievement as the key outcome variable, 7377 Icelandic adolescents were surveyed for cigarette smoking, alcohol use, daytime sleepiness, caffeine use, and potential confounders. Structural equation modeling (SEM) was used to examine direct and indirect effects of measured and latent variables in two models: the first with caffeine excluded and the second with caffeine included. A substantial proportion of variance in academic achievement, which might otherwise have been attributed to the harmful effects of cigarette smoking and alcohol use, was found to be attributable to caffeine. Evidence was obtained that daytime sleepiness, which was found to be independently associated with usage of licit substances (nicotine and alcohol) and caffeine, may be an important mediator of the negative impact of those substances on academic achievement. Findings suggest the importance of including measurements of caffeine consumption in future studies of adolescent substance use.

People Use Self-Control to Risk Personal Harm: An Intra-Interpersonal Dilemma

People will smoke cigarettes, drink alcohol, binge eat, drink coffee, eat chili peppers, fail tests, steal, ingest illicit drugs, engage in violent and sadistic actions including killing, have sex, and seek to become HIV positive for the sake of interpersonal acceptance. The self-control for personal harm model reconceptualizes behaviors that have both urge and control components as demonstrating either successful or failed self-control, depending on the incipient urge. The model underscores the role of expected social rewards as an important incentive for which people sometimes engage in personally risky and aversive behaviors despite feeling that they would rather avoid the behaviors and attendant harm. Research from diverse perspectives converges to show that risky behaviors, which might on the surface appear to be self-control failures, can in fact require self-control exertion.

SPECT assessment of brain activation induced by caffeine: no effect on areas involved in dependence

Caffeine is not considered addictive, and in animals it does not trigger metabolic increases or dopamine release in brain areas involved in reinforcement and reward. Our objective was to measure caffeine effects on cerebral perfusion in humans using single photon emission computed tomography with a specific focus on areas of reinforcement and reward. Two groups of nonsmoking subjects were studied, one with a low (8 subjects) and one with a high (6 subjects) daily coffee consumption. The subjects ingested 3 mg/kg caffeine or placebo in a raspberry-tasting drink, and scans were performed 45 min after ingestion. A control group of 12 healthy volunteers receiving no drink was also studied. Caffeine consumption led to a generalized, statistically nonsignificant perfusion decrease of 6% to 8%, comparable in low and high consumers. Compared with controls, low consumers displayed neuronal activation bilaterally in inferior frontal gyrus-anterior insular cortex and uncus, left internal parietal cortex, right lingual gyrus, and cerebellum. In high consumers, brain activation occurred bilaterally only in hypothalamus. Thus, on a background of widespread low-amplitude perfusion decrease, caffeine activates a few regions mainly involved in the control of vigilance, anxiety, and cardiovascular regulation, but does not affect areas involved in reinforcing and reward.

Association of the anxiogenic and alerting effects of caffeine with ADORA2A and ADORA1 polymorphisms and habitual level of caffeine consumption

Caffeine, a widely consumed adenosine A(1) and A(2A) receptor antagonist, is valued as a psychostimulant, but it is also anxiogenic. An association between a variant within the ADORA2A gene (rs5751876) and caffeine-induced anxiety has been reported for individuals who habitually consume little caffeine. This study investigated whether this single nucleotide polymorphism (SNP) might also affect habitual caffeine intake, and whether habitual intake might moderate the anxiogenic effect of caffeine. Participants were 162 non-/low (NL) and 217 medium/high (MH) caffeine consumers. In a randomized, double-blind, parallel groups design they rated anxiety, alertness, and headache before and after 100 mg caffeine and again after another 150 mg caffeine given 90 min later, or after placebo on both occasions. Caffeine intake was prohibited for 16 h before the first dose of caffeine/placebo. Results showed greater susceptibility to caffeine-induced anxiety, but not lower habitual caffeine intake (indeed coffee intake was higher), in the rs5751876 TT genotype group, and a reduced anxiety response in MH vs NL participants irrespective of genotype. Apart from the almost completely linked ADORA2A SNP rs3761422, no other of eight ADORA2A and seven ADORA1 SNPs studied were found to be clearly associated with effects of caffeine on anxiety, alertness, or headache. Placebo administration in MH participants decreased alertness and increased headache. Caffeine did not increase alertness in NL participants. With frequent consumption, substantial tolerance develops to the anxiogenic effect of caffeine, even in genetically susceptible individuals, but no net benefit for alertness is gained, as caffeine abstinence reduces alertness and consumption merely returns it to baseline.

The Health Effect of Psychostimulants: A Literature Review

Prevalence of psychostimulant use is high, and raising in several countries. Nicotine is the legal stimulant causing the most important public health impact. Cocaine ranks among the most used illicit substances after cannabis. Stimulant medications are frequently misused. Psychostimulants can lead to addiction, have physical, psychological and social health consequences and can induce a great disease burden. The aim of the present article is to provide a literature review on the health effects of stimulants as potential drugs of abuse. It will cover essentially cocaine, amphetamines and its derivatives (including methamphetamines and 3-4-methylenedioxymethamphetamine, ecstasy), nicotine, caffeine and khat, and touch upon the issues of prescribed substances (anti-depressants, weight control medications, attention-deficit hyperactivity disorder medications, hypersomniac disorder). Their pharmacology, addictive potential, health consequences and treatment will be discussed. We used Medline for the literature review from 1990 to the date of this review, and mention the findings of human and animal studies (the latter only if they are of clinical relevance).

Areca nut dependence among chewers in a South Indian community who do not also use tobacco

AIMS

Previously reported research suggests a dependence syndrome for areca nut use, though well-designed studies are virtually non-existent. The goal of this study was to examine evidence of areca dependence in a sample of areca-only (i.e. no tobacco) chewers using modified measurement scales.

DESIGN

A purposive sample of chewers, identified via local informants and advertisements, was surveyed from January to March of 2005.

SETTING

Six villages in Dakshina Kannada District, Karnataka State, India.

PARTICIPANTS

Fifty-nine daily areca chewers who do not also currently use any form of tobacco.

MEASUREMENTS

Questionnaires included modified versions of the Fagerström Tolerance Questionnaire, Cigarette Dependence Scale (CDS-5) and the Smokeless Tobacco Dependence Scale (STDS). Additional questions assessed demographic characteristics and patterns of use.

FINDINGS

Approximately half of respondents reported 1-3 chews/day (mean = 1.9; SD = 0.98). The average number of chewing episodes/day was 4.4 (SD = 3.4) and the average number of nuts/day was 1.2 (SD = 1.1). Users' typical chew lasts up to 20 minutes and includes spitting out the juices and rinsing the mouth with water. Overall, the levels of reported dependence symptoms were quite low, but approximately 44% of chewers endorsed at least one of the following items: continued use despite illness or mouth wounds, difficulty refraining from chewing in forbidden places, or craving during periods of abstinence. Approximately 15.4% of chewers reported at least one intentional quit attempt and a subset had summary scores indicative of dependence (13.6% had scores >16 on the CDS-5 and 5.3% had scores >11 on the STDS). Dependence scores were positively correlated with frequency of chews/day.

CONCLUSIONS

The symptoms of dependence observed in a subset of areca-only chewers warrant further investigation. Next steps should include well-controlled laboratory evaluation of dependence features.

Caffeine abstinence: an ineffective and potentially distressing tinnitus therapy

The effect of phased caffeine withdrawal and abstention on tinnitus severity was assessed using a pseudo-randomized, double-blinded, placebo-controlled crossover trial of 30 days duration. Sixty-six volunteers who experienced tinnitus and who usually consumed at least 150 mg/day of caffeine participated. The intervention was a direct replacement of usual caffeinated tea/coffee with double-blinded supplies, under one of two conditions. Condition 1: Maintenance followed by phased withdrawal. Condition 2: Phased withdrawal followed by reintroduction and maintenance. Tinnitus severity was measured by the total score of the Tinnitus Questionnaire on Days 1, 15, and 30. Secondary measures included twice daily self-rated symptoms relevant to tinnitus and caffeine withdrawal. Caffeine had no effect on tinnitus severity, the mean difference between caffeinated and decaffeinated days being -0.04 (95% confidence interval -1.99 to 1.93), p=0.97. Significant acute adverse symptoms of caffeine withdrawal were observed. No evidence was found to justify caffeine abstinence as a therapy to alleviate tinnitus, but acute effects of caffeine withdrawal might add to the burden of tinnitus.

Caffeine and a selective adenosine A2A receptor antagonist induce sensitization and cross-sensitization behavior associated with increased striatal dopamine in mice

Background

Caffeine, a nonselective adenosine A₁ and A_2A receptor antagonist, is the most widely used psychoactive substance in the world. Evidence demonstrates that caffeine and selective adenosine A_2A antagonists interact with the neuronal systems involved in drug reinforcement, locomotor sensitization, and therapeutic effect in Parkinson's disease (PD). Evidence also indicates that low doses of caffeine and a selective adenosine A_2A antagonist SCH58261 elicit locomotor stimulation whereas high doses of these drugs exert locomotor inhibition. Since these behavioral and therapeutic effects are mediated by the mesolimbic and nigrostriatal dopaminergic pathways which project to the striatum, we hypothesize that low doses of caffeine and SCH58261 may modulate the functions of dopaminergic neurons in the striatum.

Methods

In this study, we evaluated the neuroadaptations in the striatum by using reverse-phase high performance liquid chromatography (HPLC) to quantitate the concentrations of striatal dopamine and its metabolites, dihydroxylphenylacetic acid (DOPAC) and homovanilic acid (HVA), and using immunoblotting to measure the level of phosphorylation of tyrosine hydroxylase (TH) at Ser31, following chronic caffeine and SCH58261 sensitization in mice. Moreover, to validate further that the behavior sensitization of caffeine is through antagonism at the adenosine A_2A receptor, we also evaluate whether chronic pretreatment with a selective adenosine A_2A antagonist SCH58261 or a selective adenosine A₁ antagonist DPCPX can sensitize the locomotor stimulating effects of caffeine.

Results

Chronic treatments with low dose caffeine (10 mg/kg) or SCH58261 (2 mg/kg) increased the concentrations of dopamine, DOPAC and HVA, concomitant with increased TH phosphorylation at Ser31 and consequently enhanced TH activity in the striatal tissues in both caffeine- and SCH58261-sensitized mice. In addition, chronic caffeine or SCH58261 administration induced locomotor sensitization, and locomotor cross-sensitization to caffeine was observed following chronic treatment of mice with SCH58261 but not with DPCPX.

Conclusions

Our study demonstrated that low dosages of caffeine and a selective adenosine A_2A antagonist SCH58261 elicited locomotor sensitization and cross-sensitization, which were associated with elevated dopamine concentration and TH phosphorylation at Ser31 in the striatum. Blockade of adenosine A_2A receptor may play an important role in the striatal neuroadaptations observed in the caffeine-sensitized and SCH58261-sensitized mice.

Outcomes of self-help efforts in anxiety disorders

Anxiety disorders are prevalent mental disorders that are a significant burden on the community. There are effective treatments available, but many people do not seek treatment and there is a lack of professionals available to provide evidence-based treatment to all those with anxiety disorders. Recently, there has been increased attention on ways to cost effectively meet the demand for treatment with minimal cost to health services. Self-help efforts have been proposed to play a role, either as an initial minimal treatment in stepped-care models of treatment, or as strategies undertaken by an individual to prevent a full disorder developing. This review examines what is known from randomized controlled trials about the efficacy of self-help interventions for anxiety disorders.

A comparison of the effects of caffeine following abstinence and normal caffeine use

RATIONALE

Caffeine typically produces positive effects on mood and performance. However, tolerance may develop following habitual use, and abrupt cessation can result in withdrawal symptoms, such as fatigue. This study investigated whether caffeine has a greater stimulant effect in a withdrawn state compared to a normal caffeinated state, among moderate daily caffeine consumers.

MATERIALS AND METHODS

Using a within-subjects design, 17 caffeine consumers (mean +/- sd = 375 +/- 101 mg/day) ingested placebo or caffeine (250 mg) following 30-h of caffeine abstention or normal dietary caffeine use on four separate days. Self-reported mood and performance on choice reaction time, selective attention, and memory tasks were measured.

RESULTS

Caffeine had a greater effect on mood and choice reaction time in the abstained state than in the normal caffeinated state, but caffeine improved selective attention and memory in both states.

CONCLUSIONS

Although improvements in mood and reaction time may best explained as relief from withdrawal symptoms, other performance measures showed no evidence of withdrawal and were equally sensitive to an acute dose of caffeine in the normal caffeinated state.

Caffeine's implications for women's health and survey of obstetrician-gynecologists' caffeine knowledge and assessment practices

OBJECTIVE

Caffeine has relevance for women's health and pregnancy, including significant associations with spontaneous abortion and low birth weight. According to scientific data, pregnant women and women of reproductive age should be advised to limit their caffeine consumption. This article reviews the implications of caffeine for women's psychological and physical health, and presents data on obstetrician-gynecologists' (ob-gyns) knowledge and practices pertaining to caffeine.

METHODS

Ob-gyns (N = 386) who are members of the American College of Obstetricians and Gynecologists' Collaborative Ambulatory Research Network responded to a 21-item survey about caffeine.

RESULTS

Although most knew that caffeine is passed through breast milk, only 24.8% were aware that caffeine metabolism significantly slows as pregnancy progresses. Many respondents were not aware of the caffeine content of commonly used products, such as espresso and Diet Coke, with 14.3% and 57.8% indicating amounts within an accurate range, respectively. Furthermore, ob-gyns did not take into account large differences in caffeine content across different caffeinated beverages with most recommending one to two servings of coffee or tea or soft drinks per day. There was substantial inconsistency in what was considered to be "high levels" of maternal caffeine consumption, with only 31.6% providing a response. When asked to indicate the risk that high levels of caffeine have on various pregnancy outcomes, responses were not consistent with scientific data. For example, respondents overestimated the relative risk of stillbirths and underestimated the relative risk of spontaneous abortion. There was great variability in assessment and advice practices pertaining to caffeine. More than half advise their pregnant patients to consume caffeine under certain circumstances, most commonly to alleviate headache and caffeine withdrawal.

CONCLUSIONS

The data suggest that ob-gyns could benefit from information about caffeine and its relevance to their clinical practice. The development of clinical practice guidelines for caffeine may prove to be useful.