Does caffeine counteract alcohol-induced impairment? The ironic effects of expectancy

OBJECTIVE: Studies have shown that expectations of alcohol-induced impairment can produce adaptive responses to alcohol that reduce the degree of behavioral impairment displayed. The present study tested psychomotor performance following combined caffeine and alcohol administration in 42 social drinkers (23 men). Subjects were led to expect either that caffeine would antagonize alcohol-induced impairment or that it would have no effect. The study tested the hypothesis that drinkers who expected an antagonist effect of caffeine would display greater alcohol impairment than those who expected no antagonist effect. METHOD: Groups practiced a pursuit rotor task and received a moderate dose of alcohol (0.65 g/kg) combined with either 4.0 mg/kg caffeine or placebo caffeine. Some groups were led to expect that caffeine would counteract the impairing effect of alcohol and others were led to expect no counteracting effect. Psychomotor performance was then tested over a 3-hour period. RESULTS: In accord with the hypothesis, groups led to expect counteracting effects of caffeine displayed greater impairment than those led to expect no counteraction. Caffeine had no significant antagonist effect on alcohol impairment. CONCLUSIONS: The findings suggest that compensation for alcohol impairment occurs when drinkers hold clear expectations that the drug will disrupt performance. When no such clear expectation exists, no compensatory response occurs and the impairing effects of alcohol are observed.     

Social drinkers underestimate the additive impairing effects of alcohol and visual degradation on behavioral functioning

Rationale Studies have shown that social drinkers are poor estimators of alcohol-induced impairment. Underestimates of blood alcohol concentration and other indices of intoxication are associated with decisions to perform risky behaviors, such as operating a motor vehicle. It is possible that self-evaluations of impaired functioning under alcohol might be particularly compromised in the presence of other sources of impairment. A common source of impairment that co-occurs with alcohol is visual degradation.Objectives The present study compared actual and self-evaluated impairment in response to four conditions (0.65 g/kg alcohol, degradation of task-relevant stimuli, alcohol plus visual degradation, and no-treatment control) to determine whether social drinkers would perceive an increase in impairment from the combined treatments.Methods Actual psychomotor impairment was measured in 16 social drinkers (eight men) by a pursuit rotor task and their self-evaluations of this impairment were obtained on a rating scale.Results Alcohol and visual degradation impaired participants actual performance to a similar degree and, in combination, the impairing effects were additive. Participants self-evaluation ratings showed that they underestimated the additive impairment produced by the combination of alcohol and visual degradation.Conclusions The findings suggest that social drinkers might be unable to appreciate an increase in behavioral impairment when alcohol is consumed in the context of another impairing influence.     

Differential response to alcohol in light and moderate female social drinkers

Individuals who are moderate drinkers are at increased risk to abuse alcohol. Moreover, women are more vulnerable than men to the adverse consequences of alcohol consumption and recent data indicate that the drinking pattern in women is becoming more similar to that of men. However, few studies have determined whether female moderate drinkers (MD) show a differential response to the subjective and performance effects of alcohol, compared to female light drinkers (LD). Fifteen female MD who consumed an average of 34.7 drinks/month were compared to 15 female LD who consumed an average of 6.7 drinks/month. None of the participants had a first-degree family history of alcoholism or substance abuse. The acute effects of alcohol (0, 0.25, 0.50, 0.75 mg/kg) were evaluated using a double-blind, placebo-controlled outpatient design. Drug effects were assessed using a full range of performance measures, subjective-effects questionnaires and observer ratings. Alcohol impaired performance in a dose-related manner on all performance tasks for both groups of females. However, MD were less impaired than LD on balance and Digit Symbol Substitution Test (DSST). This reduced response was also evident from the observer ratings, with MD being viewed as less impaired by alcohol than LD. While ratings of Drug Liking increased in both groups of women on the ascending limb of the breath alcohol curve, alcohol was disliked by LD on the descending limb and LD reported increased ratings of Bad Drug Effects following the high dose of alcohol. The reduced performance impairment, coupled with the positive subjective effects and relative absence of adverse subjective effects, suggestive of behavioral tolerance, could result in a progression towards increased alcohol consumption among moderate female social drinkers.     

The development of alcohol tolerance: acute recovery as a predictor

Two experiments examined individual differences in the rate of alcohol tolerance development as a function of acute recovery. Male social drinkers (n=18) were trained on a complex psychomotor task and subsequently returned for four drinking sessions in which they received the same dose (0.84 ml absolute alcohol/kg) and performed the task at intervals while blood alcohol concentrations (BAC) rose and fell (peak BAC=77.2 mg/dl). A subject's acute recovery from the impairing effect of alcohol during session 1 was measured by the difference in his performance at the same BAC on the rising and the falling limb of the curve. Rate-of-tolerance development was measured by the rate of change in the subject's average impairment under the alcohol during sessions 1–4. Acute recovery scores in both experiments significantly predicted the rate at which tolerance developed, accounting for 64% of the variance in these scores (P<0.0001). Subjects who displayed more acute recovery developed tolerance more quickly. The evidence was considered to imply that the same process may give rise to both acute recovery and tolerance.     

Alcohol-induced performance impairment in heavy episodic and light social drinkers

OBJECTIVE: The purpose of this study was to examine performance effects of alcohol in young adult heavy drinkers (HDs) and light drinkers (LDs). Prior research has shown that HDs have alterations in subjective alcohol response in comparison with LDs, with greater reported stimulant-like effects and reduced sedative-like effects. It is unclear whether these quantitative differences extend to performance and objective effects. METHOD: Thirty-four subjects participated (20 HDs and 14 LDs) in three early evening individual alcohol challenge sessions. Subjects were examined on eye movement and psychomotor performance tasks before and several times after consuming either 0.8 g/kg or 0.4 g/kg ethanol or placebo beverage. RESULTS: Alcohol produced similar impairment for the groups in psychomotor performance and saccadic velocity measures, with blood alcohol concentration dependent group differences on the smooth pursuit task and a marginally lower threshold for impairment for HDs on the saccadic latency task. Covarying for personality differences (i.e., disinhibition and boredom susceptibility traits) and family history of alcoholism did not significantly alter the findings. CONCLUSIONS: Despite prior findings of differential subjective response to alcohol in HDs and LDs, alcohol-induced performance impairment was comparable between the groups. Our findings suggest HDs may be particularly at risk for alcohol-related consequences because their greater sensitivity to positive alcohol effects and/or tolerance to sedative effects may not be accompanied by a lesser degree of alcohol-induced performance impairment.     

Effects of naltrexone pretreatment on the subjective and performance effects of ethanol in social drinkers

Clinical trials suggest that opioid antagonists may be effective in the treatment of alcoholism. For example, two recent clinical trials reported that alcoholics treated with the opioid antagonist naltrexone exhibited higher abstinence rates, decreased craving and a decrease in the amount of alcohol consumed if drinking occurred. The present study examined the hypothesis that naltrexone pretreatment would attenuate the behavioral responses to an acute dose of ethanol in normal, healthy social drinkers. Thirteen healthy male and female social drinkers participated in a six-session, double-blind, placebo-controlled, crossover design study. On each session, subjects ingested a capsule containing naltrexone (25 or 50mg) or placebo and one hour later consumed a beverage containing ethanol (0.5g/kg) or placebo. For three hours after the beverage was consumed, breath alcohol levels were measured and subjects completed standardized subjective effects questionnaires and performance tasks at regular intervals. Ethanol alone produced its prototypic effects, including positive subjective responses such as euphoria and increased ratings of overall liking, as well as increased ratings of confusion. Ethanol also impaired performance on a verbal recall task. Naltrexone alone produced few subjective effects and did not impair psychomotor or verbal recall performance. Contrary to our hypothesis, pretreatment with naltrexone did not alter the positive subjective effects, or any other effects, of ethanol. Further research is needed to determine the influence of factors such as baseline level of ethanol consumption or duration of naltrexone treatment on the interaction between ethanol and the endogenous opioid system.     

Social drinking history,behavioral tolerance and the expectation of alcohol

This research tested the hypothesis that a compensatory response to cues for alcohol contributes to the greater behavioral tolerance displayed by more experienced social drinkers. Sixty male social drinkers, ranging from 19 to 24 years of age, participated in the study. Thirty subjects had been drinking for 20 months or less (mean=11.0 months), and were classified as novice (N) drinkers. The remaining 30 subjects had been drinking for 24 months or more (mean=40.8 months), and were classified as experienced (E) drinkers. All subjects practiced a pursuit rotor task that measured psychomotor skill. Equal numbers of E and N subjects were then assigned to one of three groups (n=10). Two groups were led to expect, alcohol and performed the task after receiving either 0.56 g/kg alcohol, or a placebo. The third group received no beverage. E subjects displayed more behavioral tolerance to alcohol than did N drinkers. In accord with the hypothesis E drinkers displayed a drug-opposite improvement in performance under a placebo, whereas N drinkers showed no appreciable change in performance. These observations support the hypothesis that the acquisition of a compensatory response to cues predicting the administration of alcohol contributes to the greater behavioral tolerance of more experienced drinkers.     

Behavioral effects of alcohol in novice and experienced drinkers: alcohol expectancies and impairment

This study was designed to test the hypothesis that the relation between an individual's expected and actual impairment under alcohol develops as a function of drinking experience. Fourteen early stage, novice (N) and 14 experienced (E) male social drinkers participated in the research. Group N had been drinking for 20 months or less (mean =8.1 months). Group E subjects had been drinkers for 24 or more (mean =42.7 months). All subjects practised a task that measured psychomotor skill (pursuit rotor) and rated the degree to which alcohol was expected to impair their performance on the task. Half of the subjects in each group then performed the task under alcohol (0.56 g/kg). The remainder served as controls and received no beverage prior to performing the task. In accord with the hypothesis, experienced drinkers who expected more impairment performed more poorly under alcohol, whereas novice drinkers' expected and actual impairment were not related. In addition, when novice and experienced drinkers received no beverage, their expectations were unrelated to their drug-free performance. Thus alcohol expectancies were not relevant to performance in a non-drinking situation. These findings contribute new information identifying drinking history as an important factor strengthening the relationship between expectations about the effect of alcohol and behavior under the drug.     

Social drinking history,behavioral tolerance and the expectation of alcohol

This research tested the hypothesis that a compensatory response to cues for alcohol contributes to the greater behavioral tolerance displayed by more experienced social drinkers. Sixty male social drinkers, ranging from 19 to 24 years of age, participated in the study. Thirty subjects had been drinking for 20 months or less (mean?=?11.0 months), and were classified as novice (N) drinkers. The remaining 30 subjects had been drinking for 24 months or more (mean = 40.8 months), and were classified as experienced (E) drinkers. All subjects practiced a pursuit rotor task that measured psychomotor skill. Equal numbers of E and N subjects were then assigned to one of three groups (n?=?10). Two groups were led to expect alcohol and performed the task after receiving either 0.56?g/kg alcohol, or a placebo. The third group received no beverage. E subjects displayed more behavioral tolerance to alcohol than did N drinkers. In accord with the hypothesis, E drinkers displayed a drug-opposite improvement in performance under a placebo, whereas N drinkers showed no appreciable change in performance. These observations support the hypothesis that the acquisition of a compensatory response to cues predicting the administration of alcohol contributes to the greater behavioral tolerance of more experienced drinkers.     

Lack of tolerance to the disinhibiting effects of alcohol in heavy drinkers

Rationale

Alcohol tolerance is observed as a diminished response to a given dose as a function of repeated administrations of the drug. Research has consistently shown that heavier drinkers display reduced reactions to alcohol (i.e., tolerance) compared with lighter drinkers. However, the majority of this work has focused primarily on measures of motor performance, whereas the development of tolerance to alcohol's impairing effects on cognitive processes, such as inhibitory mechanisms of behavioral control, remains relatively unexplored.

Objective

The purpose of the present study was to examine the relationship between drinking habits and the degree to which alcohol affects drinkers' inhibitory control and motor coordination.

Methods

Fifty-two non-dependent drinkers reported their recent drinking patterns. Their inhibitory control and motor coordination were measured in response to placebo and 0.65?g/kg alcohol.

Results

Alcohol significantly impaired inhibitory control and motor coordination compared with placebo. Moreover, greater quantity and frequency of recent consumption predicted less alcohol impairment of motor coordination. However, there was no relationship between recent drinking habits and the degree of impairment of inhibitory control.

Conclusions

These findings suggest that tolerance to the disinhibiting effects of alcohol might not readily develop as a result of recent, heavy drinking.     

Compensating for alcohol-induced impairment: alcohol expectancies and behavioral disinhibition

OBJECTIVE: Studies have shown that expectations of alcohol-induced impairment can produce adaptive responses to alcohol that serve to reduce the degree of behavioral impairment displayed. The present research examined how an expectancy-induced adaptive response could reduce the impairing effects of alcohol on response activation, while at the same time increase its impairing effect on response inhibition. METHOD: Social drinkers (N = 48) practiced a stop-signal choice reaction time (RT) task that measured their speed of responding and their ability to inhibit responses to stop signals. Subjects then received 0.65 g/kg of alcohol, a placebo beverage, or no beverage. Prior to performing the task again, one-half of the sample was given information to expect that alcohol would slow (i.e., impair) their RT. The others received no expectancy treatment. RESULTS: Subjects led to expect slowed RT displayed faster RTs but fewer inhibitions under alcohol, compared with those who received no such expectancy The same pattern of results was observed under the placebo condition. In the "no beverage" condition, the expectancy treatment had no significant effect on subjects' RT or inhibitions. CONCLUSIONS: The findings demonstrate that an alcohol expectancy can reduce impairment of one aspect of performance under the drug while increasing its impairing effect on another. The study contributes to a growing body of research that highlights the importance of understanding interactions between the expected and pharmacological effects of alcohol.     

Situational determinants of alcohol abuse among Caucasian and African-American college students

The present study examined gender, race, and binge status differences in alcohol consumption among Caucasian and African-American college students as well as situational differences as qualified by the race of binge drinkers. A confidential questionnaire was voluntarily completed by Caucasians (n = 102) and African-Americans (n = 81) at a medium-sized regional university. The data analysis revealed a significant gender effect on alcohol consumption, with men consuming more alcohol than women. There was no significant main effect of race on alcohol consumption. In addition, Caucasian binge drinkers had significantly higher interpersonal problem behavior scores than did binge-drinking African-Americans, and binge-drinking African-Americans had higher intrapersonal problem behavior scores than did binge-drinking Caucasians.     

Do Alcohol Consumption Patterns of Adolescents Differ by Beverage Type?

ABSTRACT

The overall purpose of this study was to explore the alcohol consumption patterns of adolescents by beverage type. A total of 705 primarily 9th grade students were recruited to participate in this study in the spring of 2002. Alcoholic beverage use differed significantly across gender and ethnicity on a number of beverage-specific drinking measures, including initiation, quantity and frequency, binge drinking, chugging, and alcohol problems (p's<.05). Stepwise discriminant analyses indicated that drug use and social beliefs were notably important in discriminating adolescent drinkers from non-drinkers of specific alcoholic beverages. This study's results indicate the need for testing interventions tailored to alcohol consumption patterns including beverage type.     

Protracted impairment of impulse control under an acute dose of alcohol: A time-course analysis

Alcohol is well-known for impairing impulse control as well as its disruptive effects on other aspects of behavioral functioning, such as motor control. Time-course analyses during a single dose show rapid development of acute tolerance to impairment of motor coordination, reaction time, and levels of subjective intoxication, but no acute tolerance to impairment of the ability to inhibit responses. Evidence for a possible lag in tolerance development to the impairing effects of alcohol on inhibitory control suggests that, as drinkers' blood alcohol concentration (BAC) declines, they might exhibit prolonged impulsivity despite having an unimpaired ability to initiate action. The present study extended the time-course analysis to examine the recovery of inhibitory control under a dose of alcohol as drinkers' BAC descended from a peak of 80 mg/100 ml to a zero level. Twenty-four healthy adults were tested following 0.65 g/kg alcohol and a placebo in a counterbalanced order. They performed a cued go/no-go task that measured response inhibition. They also performed tasks that assessed reaction time, motor coordination, and completed ratings of their subjective levels of intoxication. Alcohol initially impaired inhibitory control, response time, and motor coordination and increased subjective ratings of intoxication. However, acute tolerance to the impairing effects of alcohol was observed for measures of response time, motor coordination, and ratings of intoxication and these measures returned to sober (i.e., placebo) levels by the time BAC fell to near zero. By contrast, impairment of inhibitory control showed no acute tolerance and remained impaired even when drinkers' BAC returned to near zero. Taken together, these results indicate that the disinhibiting effects of alcohol are present even when the impairing effects of alcohol on other aspects of behavior have diminished under the dose. These findings could provide a greater understanding of impulsive behaviors during the descending limb of intoxication.     

Effects of 0.4 g/kg alcohol on attentional bias and alcohol-seeking behaviour in heavy and moderate social drinkers

Alcohol intoxication is known to influence attentional biases for alcohol-related cues and alcohol-seeking behaviour. It is unknown if heavier drinkers are more or less sensitive to these effects of alcohol, or whether the effects of alcohol on attentional bias are associated with subsequent alcohol-seeking behaviour. In the present study, 55 social drinkers were administered either 0.4?g/kg alcohol or placebo in a repeated measures, double-blind experimental design. Participants completed a visual probe task with eye movement monitoring (to measure attentional bias) and a bogus taste test (to measure alcohol-seeking) in both alcohol and placebo sessions. Heavy drinkers showed an attentional bias for alcohol cues that was unaffected by alcohol, whereas in moderate drinkers attentional bias was present after alcohol administration, but was absent after placebo. All participants voluntarily consumed more beer during the taste test after administration of alcohol compared with placebo. The effects of alcohol on attentional bias were unrelated to the effects of alcohol on beer consumption. Results are consistent with the development of tolerance, rather than sensitization, to the acute effects of alcohol on attentional biases in heavy drinkers. However, alcohol-induced increases in attentional bias were not related to the effects of alcohol on the motivation to drink.     

Binge drinking in university students: A test of the cognitive model

The aim of this study was to test the cognitive model [Addict. Behav. 29 (2004) 159] of binge drinking in university students. In Study 1, 202 participants completed the Drinking Expectancy Questionnaire (DEQ), the Drinking Refusal Self-Efficacy Questionnaire (DRSEQ), and the Khavari Alcohol Test (KAT). The results showed that both alcohol expectancies (AEs) and drinking refusal self-efficacy (DRSE) are needed to discriminate between binge, social, and heavy drinkers. In general, binge drinkers tend to have higher AEs than social drinkers, and have slightly lower DRSE. However, young social and binge drinkers can only be discriminated on the basis of their AEs. One hundred and fourteen students were recruited for the second study, to predict which individuals would engage in binge drinking during a 4-week self-monitoring period. Over 80% of predicted binge drinkers binged at least once during the monitoring period. These two studies confirmed the cognitive model of binge drinking, and thus, hold implications for the prevention of binge drinking among adolescents and young adults.     

Is behavioral tolerance learned?

Both scientific and anecdotal evidence indicates that social drinkers can develop resistance (i.e., behavioral tolerance) to alcohol's impairing effects over time. Although repeated exposure to alcohol is thought to explain tolerance development on a physiological level, the acquisition of behavioral tolerance appears to involve additional factors. In particular, learned associations between a drinker's behavior following alcohol consumption and the subsequent consequences may play an important role. When favorable consequences result from displaying unimpaired (i.e., tolerant) behavior after drinking, a drinker learns to develop behavioral strategies to compensate for alcohol's effects. In contrast, if a drinker does not receive a reward for unimpaired behavior--or finds that a more favorable outcome follows the display of intoxicated behavior--tolerance does not develop. Studies show that subjects also can develop behavioral tolerance to alcohol when they practice a task while impaired by factors other than alcohol or when they mentally rehearse task performance while under the influence of alcohol.     

Behavioral responses to ethanol in light and moderate social drinkers following naltrexone pretreatment

The opioid antagonist naltrexone has been shown to be effective in the treatment of alcoholism, possibly by dampening the subjective effects of ethanol. However, naltrexone does not consistently attenuate the effects of ethanol in social drinkers in laboratory-based challenge studies. In the present study, 25 healthy volunteers, who were either light drinkers (mean=3 drinks per week) or moderate drinkers (mean=16 drinks per week), participated in six evening sessions. At each session, subjects ingested a capsule containing naltrexone (25 or 50 mg) or placebo, and 1 hr later they consumed a beverage containing ethanol (0.25 g/kg, equivalent to about two standard alcoholic drinks) or placebo. Subjects received all combinations of pretreatments and beverages. They completed self-report mood questionnaires and psychomotor tests at regular intervals. This low dose of ethanol produced modest but significant effects on self-report measures such as ratings of feeling a drug effect and of liking the drug effect. However, naltrexone (25 or 50 mg) pretreatment had no dampening effect on subjects' responses to ethanol. These results indicate that acute doses of naltrexone that are effective when administered chronically to alcoholics do not attenuate the acute effects of a low dose of ethanol in non-problem drinkers.     

The problem of binge drinking among Italian university students: a preliminary investigation

Although binge drinking and excessive alcohol consumption are relevant public health problems in Italy, no research has been carried out on those topics for years. In the first months of the year 2005, 1000 undergraduates in a number of Italian universities were administered a survey regarding their attitudes in alcohol consumption. Participants were to complete a questionnaire including demographic and alcohol variables, the Sensation-Seeking Scale (SSSV) and the Positive Drinking Expectancy Scale (PDMS). According to previous research, students were categorized in non-drinkers, social, binge, and heavy drinkers. Results showed that the estimated percentage of binge drinking among university students is 32.9%. The survey revealed-by means of univariate and multivariate analysis-that social, binge, and heavy drinkers differ in terms of some drinking variables, in their expectancies about alcohol and in sensation-seeking dimensions. Implications for the prevention of binge drinking in young adults are currently under discussion even if further investigation into the Italian context is urgently needed.     

Empirical separation of physiologic and expected effects of alcohol on complex perceptual motor performance

The role of expectancy in producing perceptual motor-performance deficits following alcohol consumption was investigated in a 2 × 2 factorial experiment. Forty male normal drinkers (1) either were or were not administered 0.414 g ethanol/kg body weight and (2) either were or were not instructed they were consuming an alcoholic beverage (regardless of actual beverage content). Performance on a divided-attention task requiring simultaneous pursuit rotor tracking and choice reaction-time responding provided the main dependent measures. Alcohol disrupted tracking performance and interacted with instructions regarding beverage content to influence choice reaction-time performance. Results confirmed previous reports of divided-attention task performance deficits induced by a low alcohol dose, but, more importantly, indicated that subjects' expectancies also influence performance levels. These findings demonstrate the importance of controlling for expectancy effects in alcohol research, and suggest that alcohol and expectancy may influence perceptual motor performance through different processes.