Individual Differences in Behavioral and Subjective Responses to Alcohol

The reinforcing properties and subjective effects of alcohol were assessed in 29 normal volunteers using a seven-session choice procedure. On the first four sessions, subjects sampled an alcohol (0.5 g/kg) and a placebo beverage twice each. On three subsequent choice sessions, subjects chose the drink they preferred. The number of times they chose alcohol was the measure of its reinforcing properties. On all sessions subjects completed mood questionnaires before and several times after consuming the beverage. Other dependent measures during the experiment included a cognitive performance task, drug liking and identification questionnaires, and breathalyzer alcohol determinations. Demographic and personality data also were obtained. Approximately one-third of the subjects chose the alcohol-containing beverage on all three choice sessions, one-third alternated in their choices of alcohol and placebo, and one-third consistently chose the placebo. When the subjective effects of alcohol (determined during sampling sessions) were compared across the three choice groups, qualitative differences in response to alcohol were observed. For example, alcohol increased elation and vigor scores in the consistent choosers of alcohol, whereas it decreased scores on these measures in the consistent placebo choosers. Consistent alcohol choosers did not differ from placebo choosers in gender or age but they reported more marijuana use and slightly more alcohol use outside the laboratory. They also scored higher on certain measures of arousal and depression, on the Sensation Seeking Scale and on the Psychopathic State Inventory. The results are discussed in terms of individual differences in vulnerability to excessive use of alcohol.     

Effects of alcohol on the response to hyperventilation of participants high and low in anxiety sensitivity

BACKGROUND: Previous research suggests that high levels of anxiety sensitivity (AS; fear of anxiety symptoms) may constitute a risk factor for alcohol abuse. The present study evaluated the hypothesis that high AS levels may increase risk for alcohol abuse by promoting a heightened sober reactivity to theoretically relevant stressors and heightened sensitivity to alcohol's emotional reactivity dampening effects, which would negatively reinforce drinking in this population. METHODS: One hundred and two undergraduate participants (51 high AS, 51 low AS) with no history of panic disorder were assigned to either a placebo, low-dose alcohol, or high-dose alcohol beverage condition (17 high AS, 17 low AS per beverage condition). After beverage consumption and absorption, participants underwent a 3 min voluntary hyperventilation challenge. RESULTS AND CONCLUSIONS: High-AS/placebo participants displayed greater affective and cognitive reactivity to the challenge than low-AS/placebo participants, which indicated increased fear and negative thoughts (e.g., "losing control") during hyperventilation among sober high AS individuals. Dose-dependent alcohol dampening of affective and cognitive reactivity to hyperventilation was observed only among high-AS participants, which suggested that high-AS individuals may be particularly sensitive to alcohol-induced reductions in their degree of fear and negative thinking in response to the experience of physical arousal sensations. In contrast, dose-dependent alcohol dampening of self-reported somatic reactivity was observed among both high- and low-AS participants. We discuss implications of these results for understanding risk for alcohol abuse in high-AS individuals, as well as directions for future research.     

The incidence and severity of hangover the morning after moderate alcohol intoxication

AIMS: To determine the incidence and covariates of hangover following a night of moderate alcohol consumption at a targeted breath alcohol level. DESIGN: Data were combined from three randomized cross-over trials investigating the effects of heavy drinking on next-day performance. A total of 172 participants received either alcoholic beverage (mean=0.115 g% breath alcohol concentration) or placebo on one night and the other beverage a week later. The next day, participants completed a hangover scale. PARTICIPANTS: Participants were 54 professional merchant mariners attending a recertification course at Kalmar Maritime Academy (Kalmar, Sweden) and 118 university students or recent graduates recruited from greater Boston. SETTING: One trial was conducted at Kalmar Maritime Academy (Sweden); the other two were conducted at the General Clinical Research Center at Boston Medical Center. MEASUREMENTS: A nine-item scale assessed hangover. FINDINGS: Hangover was reported by 76% of participants. Neither alcoholic beverage type nor participant characteristics was associated with incidence of hangover. CONCLUSIONS: Our findings on the propensity of hangover suggest that 25-30% of drinkers may be resistant to hangover.     

Alcohol affects executive cognitive functioning differentially on the ascending versus descending limb of the blood alcohol concentration curve

BACKGROUND: Executive cognitive functioning (ECF), a construct that includes cognitive abilities such as planning, abstract reasoning, and the capacity to govern self-directed behavior, has been recently researched as an antecedent to many forms of psychopathology and has been implicated in alcohol-related aggression. This study was designed to examine whether differential ECF impairments can be noted on the ascending versus the descending limbs of the blood alcohol concentration curve. METHODS: Forty-one male university students participated in this study. Twenty-one subjects were given 1.32 ml of 95% alcohol per kilogram of body weight, mixed with orange juice, and the remaining 20 were given a placebo. Participants were randomly assigned to either an ascending or descending blood alcohol group and were tested on six tests of ECF on their assigned limb. Subjective mood data were also collected. RESULTS: Intoxicated participants on both limbs demonstrated ECF impairment; the descending-limb group showed greater impairment than their ascending-limb counterparts. Intoxicated subjects were significantly more anxious at baseline than placebo subjects. The introduction of this covariate nullified any significant differences in subjective mood found on either limb of the blood alcohol concentration curve, but ECF impairments remained robust. CONCLUSIONS: Our results support the conclusion that alcohol negatively affects cognitive performance and has a differential effect on the descending versus the ascending limb of the blood alcohol concentration curve. The latter finding may have important ramifications relating to the detrimental consequences of alcohol intoxication.     

Effects of a moderate evening alcohol dose. I: sleepiness

Background: Few studies examining alcohol's effects consider prior sleep/wake history and circadian timing. We examined introspective and physiological sleepiness on nights with and without moderate alcohol consumption in well-rested young adults at a known circadian phase.
Methods: Twenty-nine adults (males=9), ages 21 to 25 years ( M =22.6, SD=1.2), spent 1 week on an at-home stabilized sleep schedule (8.5 or 9 hours), followed by 3 in-lab nights: adaptation, placebo, and alcohol. Alcohol (vodka; 0.54 g/kg for men; 0.49 g/kg for women) or placebo beverage was consumed over 30 minutes ending 1 hour before stabilized bedtime. In addition to baseline, 3 sleep latency tests (SLTs) occurred after alcohol/placebo ingestion (15, 16.5, and 18 hours after waking). Stanford Sleepiness Scales (SSS) and Visual Analog Scales (VAS) of sleepiness were completed before each SLT and approximately every 30 minutes. The Biphasic Alcohol Effects Scale (BAES) was administered a total of 4 times (baseline, 5, 60, and 90 minutes postalcohol/placebo). Subjects' circadian phase was determined from melatonin levels in saliva samples taken at approximately 30-minute intervals.
Results: All sleepiness and sedation measures increased with time awake. Only SSS and BAES sedation measures showed higher levels of sleepiness and sedation after alcohol compared with placebo. The mean circadian phase was the same for assessments at both conditions.
Conclusions: Alcohol did not increase physiological sleepiness compared with placebo nor was residual sedation evident under these conditions. We conclude that the effects on sleepiness of a moderate dose of alcohol are masked when sleep–wake homeostatic and circadian timing influences promote high levels of sleepiness.     

The balanced placebo design: effects of alcohol and beverage instructions cannot be independently assessed.

Subjects were randomly assigned to the four cells of the balanced placebo design, with 10 males and 10 females per cell. Following told-alcohol or told-no alcohol beverage instruction manipulations, participants consumed either a vodka-tonic beverage containing a dose of vodka sufficient to induce a peak blood alcohol level of 0.05% or a beverage containing only tonic water. Subjects' self-report ratings of beverage alcohol content indicated that alcohol overrode the effects of beverage instructions in the told-tonic/given-alcohol condition. It was concluded that the design cannot independently evaluate effects of both alcohol and beverage instructions when behaviorally significant alcohol doses are administered.     

The subjective, rather than the disinhibiting, effects of alcohol are related to binge drinking

Background: Evidence suggests that alcohol‐related problems are associated with impulsivity and disinhibited behavior. Less certain is whether disinhibited behavior is due to an impulsive disposition or alcohol’s ability to disinhibit some people more than others. There are a range of disinhibited behaviors associated with alcohol, including excessive alcohol consumption, bingeing. The study tested whether nondependent alcohol bingers showed more disinhibition after placebo and/or alcohol relative to nonbingers and whether this was related to enhanced motivation to drink following a priming dose of alcohol. Methods: Twenty participants (10 bingers) attended the laboratory twice. Baseline measures included impulsivity, alcohol‐related cognitions, alcohol urge, and mood. Participants were preloaded with alcohol (male: 0.6 g/kg, female: 0.5 g/kg) and placebo (counterbalanced). After a 20‐minute rest, participants completed 2 impulsivity tasks (Two Choice & Time Estimation) separated by second urge and mood ratings. Results: Bingers did not show greater impulsivity characteristics but were more concerned about their drinking (p = 0.02) and ability to control drinking (p = 0.04). A priming effect was found: alcohol urge increased after alcohol but not placebo (p = 0.006). Bingers reported greater tolerance to the sedative (p = 0.05) and lightheaded (p = 0.04) effects of alcohol, relative to nonbingers. Binge status was not associated with impulsivity task performance, while preload type (alcohol/placebo) supported only marginal associations. Conclusions: Risk of binge drinking in nondependent individuals is not strongly affected by impulsive personality characteristics or alcohol’s ability to induce behavioral disinhibition. However, alcohol did lead to a priming effect and bingers were more tolerant to the sedative and lightheaded effects of alcohol relative to placebo. Risk of binge drinking is associated with the subjective effects of a priming dose of alcohol.     

Effect of tryptophan depletion on alcohol cue-induced craving in abstinent alcoholic patients

BACKGROUND: The capacity of alcohol cues to precipitate the desire to drink may be an important determinant of relapse to alcohol use in recovering alcohol-dependent patients. This study evaluated whether attenuation of serotonin synthesis via depletion of its precursor tryptophan reduces the magnitude of cue-induced craving for alcohol in recently abstinent alcoholic individuals. METHODS: Alcohol-dependent patients (n = 16), 1 to 3 months after detoxification, who exhibited a 20% or greater increase in reported craving when presented with an alcoholic beverage, completed two additional alcohol cue-exposure test days, 1 week apart. Each cue exposure was preceded by administration of a concentrated amino acid drink that resulted in a rapid and significant decline in plasma free tryptophan (active depletion, no tryptophan supplementation) or a similar drink containing tryptophan (placebo depletion). Tests were conducted in a randomized, double-blind fashion. RESULTS: There were no significant changes in the magnitude of cue-induced craving with active tryptophan depletion compared with placebo. CONCLUSIONS: These data question the dependence of alcohol cue-induced craving in sober alcoholics on the ongoing synthesis of serotonin.     

Effects of methadone plus alcohol on cognitive performance in methadone-maintained volunteers

Background: Methadone maintenance patients (MMP) often abuse other drugs, including alcohol. The combined use of methadone and alcohol could impair performance and daily functioning. Objective: To examine the effects of methadone in combination with alcohol, as well as acute increases in methadone, on performance outcomes. Methods: This double-blind, double-dummy, crossover study included eight opioid-dependent participants stabilized on methadone. Participants completed six inpatient sessions corresponding to methadone (100% or 150% of daily dose) and beverage (placebo, 0.25 or 0.50?g/kg alcohol). Performance tasks were completed before and after drug administration. Area under the time-course values were analyzed by a 2 (methadone dose) by 3 (alcohol dose) repeated measures analysis of variance. Results: Main effects of methadone were observed for two attention outcomes, suggesting reduced accuracy and slowed responding at an elevated methadone dose. In addition, main effects of alcohol were observed for episodic memory (false alarms and response bias) suggesting more impulsive responding as alcohol dose increased. No robust interactions of methadone and alcohol were observed for any outcome. Conclusions: Study findings indicate that an acute increase in methadone (150%) and a moderate dose of alcohol (2–3 drinks) can impair distinct aspects of performance, although no significant interactive effect between methadone and alcohol was found. Future studies with larger sample sizes, larger doses, and more clinically informative tasks could expand on the present findings and further explore the cognitive consequences of concurrent opioid and alcohol use.     

Alcohol Expectancies and Behavioral and Emotional Responses to Placebo Versus Alcohol Administration

Forty normal drinking males were recruited for a study of "responses to alcohol." Following the completion of an alcohol use questionnaire that included measures of expectancies of alcohol effects, subjects were randomly assigned to either receive the actual 0.6 g/kg dose of ethanol to bring their peak blood alcohol concentration (BAC) to near 0.075 g/dl or to receive a placebo dose. Neither the subject nor the tester was aware of the condition to which the subject has been assigned. Prior to dosing and at repeated 1/2-hr intervals following dosing, subjects were tested on a battery of motor coordination, perceptual speed, reaction time, and mood measures. Significant alcohol effects were found for several measures, but the only significant interaction of individual differences in expectancies of alcohol effects with alcohol dosing occurred for self-perceived intoxication. Subjects who expected more disinhibition after alcohol dosing and who were administered alcohol reported more intoxication than those expecting less disinhibition, while no expectancy effect was found for subjects administered the placebo.     

Healthy subjects with a family history of alcoholism show increased stimulative subjective effects of alcohol

Background: Research has shown that subjects with a family history positive (FHP) of alcoholism are at increased risk for alcoholism and that this group reacts differently to alcohol than family history negative (FHN) subjects. These different levels of sensitivity may make FHP persons more likely to consume alcohol. Here, we tested the hypothesis that subjects FHP for type 1 alcoholism (according to Cloninger) are more sensitive than control subjects to the stimulative, properties of alcohol following a single moderate dose of alcohol. Methods: Fifty‐one healthy men and women (22 FHP and 29 FHN) participated in 2 laboratory sessions, in which they consumed a beverage containing ethanol (0.6 g/kg in juice) or placebo (juice alone) in a randomized order. Primary dependent measures were self‐report questionnaires of mood states. Results: Subjects with family history of type 1 alcoholism showed increased stimulative responses and an elevated positive mood state after ethanol compared to controls. Conclusions: At this moderate dose, ethanol increased stimulative subjective responses in individuals who were “family history positive.” This enhanced sensitivity could motivate to exaggerated drinking and thereby increase the risk for developing alcoholism.     

Reinforcing mood effects of alcohol in coping and enhancement motivated drinkers

BACKGROUND: People may be motivated to drink because of differential sensitivities to the rewarding outcomes of alcohol consumption. Previous research has demonstrated that alcohol may produce both potentially positive reinforcing effects (i.e., increased elation; Conrad et al., 2001) and potentially negative reinforcing effects (i.e., anxiolytic effects; Levenson st al., 1980). It was desired to test the effects of alcohol on mood in a sample of two groups of drinkers that report different motivations for alcohol use. It was hypothesized that both potentially positive and negative reinforcing mood effects would be observed and that these effects would be moderated by drinking motive. METHODS: Twenty-four drinkers with Coping Motives (CMs) and 24 drinkers with Enhancement Motives (EMs) were randomly assigned to either an alcohol condition (target blood alcohol level of 0.08%) or a placebo condition. Participants used the Profile of Mood States-Bipolar (Lorr, 1983) to report their mood at (1) sober baseline, (2) after beverage consumption, and (3) during anticipation of a self-disclosing speech (a stressor). RESULTS: As hypothesized, after drinking, those in the alcohol group reported increased feelings of elation and energy relative to sober baseline. Those receiving alcohol also reported feeling more confused and anxious after beverage consumption. Also as hypothesized, participants receiving alcohol reported feeling increased sedation during anticipation of the stressor, whereas those receiving placebo reported increased energy during this period. Contrary to the hypothesis, none of these effects were moderated by drinking motive. CONCLUSIONS: Although potentially positive and negative reinforcing mood effects of alcohol were observed, CM and EM drinkers were not differentially sensitive to these effects. However, it is possible that EM drinkers may highly value the baseline stimulating effects of alcohol, whereas CM drinkers may highly value the anxiolytic effects that were observed during anticipation of the stressor.     

Comparison of cross-sectional and daily reports in studying the relationship between depression and use of alcohol in response to stress in college students

BACKGROUND: Alcohol use in response to stress in college students may be affected by the presence of symptoms of depression. However, this is a challenging issue to study due to the various methodologies used as well as the possible effect of depressed mood on the accuracy of self-report. This study focused on methodological issues as possible sources of equivocal findings regarding the relationship between depressed mood and alcohol use in response to stress in a college student population. Findings may differ when these variables are examined cross-sectionally versus longitudinally. METHODS: Depressed mood and alcohol coping were assessed both cross-sectionally and repeatedly over time in 125 college students. Participants were assessed at baseline using a diagnostic self-report measure of depression as well as a measure of typical coping style. In addition, daily measures of stress, symptoms of depression, and coping were completed for 45 consecutive days. RESULTS: Different relationships between depressed mood and alcohol coping were found when depressed individuals were analyzed separately from those who were not depressed. Although a significant correlation between daily use of alcohol coping and daily depressed mood was found, there were no differences between depressed and nondepressed participants (as assessed at baseline) on daily alcohol coping. CONCLUSIONS: These findings have implications for research design as well as clinical assessment regarding the relationships between mood and use of alcohol for coping; the findings suggest that cross-sectional measures of mood and alcohol use may obscure differences as assessed repeatedly over time. In addition, these findings support the utility of frequent assessment of depressive symptoms when implementing or evaluating programs that target coping skills in college students.     

Effects of naltrexone during the descending limb of the blood alcohol curve

The neuropharmacological effects of alcohol are known to vary by limb of the blood alcohol curve, yet human laboratory studies of alcoholism pharmacotherapies have largely failed to consider limb of intoxication when examining medication effects on subjective responses to alcohol. This study examined the effects of naltrexone compared to placebo on subjective responses to alcohol at the descending limb of the blood alcohol curve following a controlled intravenous (IV) alcohol administration. Non-treatment-seeking hazardous drinkers (n = 38) completed two double-blind counterbalanced IV alcohol challenge sessions, one after taking naltrexone (50 mg) for three days and one after taking a placebo for three days. During each session, participants reported on subjective responses to alcohol during the descending limb of the blood alcohol curve. Analyses revealed significant main effects of naltrexone, reflecting significantly decreased alcohol-induced stimulation, craving, vigor, positive mood, and alcohol "high" and increased tension as compared to placebo. These findings suggest that naltrexone may exert some of its therapeutic effects via alterations to experiential aspects of intoxication during the descending limb of alcohol intoxication. Additionally, these results highlight the potential utility of considering limb of blood alcohol curve when examining the mechanisms of action of pharmacotherapies thought to alter subjective responses to alcohol.     

Alcohol effects on cerebral blood flow in subjects with low and high responses to alcohol

Background: Although there are multiple indications that alcohol can alter many physiological brain functions, including cerebral blood flow (CBF), studies of the latter have generally used small‐ or modest‐sized samples. Few investigations have yet evaluated how CBF changes after alcohol relate to subsets of subjects with elevated alcoholism risks, such as those with lower levels of response (LR) to alcohol. This study used arterial spin labeling (ASL) after alcohol administration to evaluate a large sample of healthy young men and women with low and high alcohol responses, and, thus, varying risks for alcohol use disorders (AUD). Methods: Healthy young adult social drinkers with low and high LR (N = 88, 50% women) matched on demography and drinking histories were imaged with whole‐brain resting ASL ～1 hour after ingesting ～3 drinks of ethanol and after a placebo beverage (i.e., 178 ASL sessions). The relationships of CBF changes from placebo to alcohol for subjects with low and high LR were evaluated. Results: CBF increased after alcohol when compared to placebo in 5 frontal brain regions. Despite identical blood alcohol concentrations, these increases with alcohol were less prominent in individuals who required more drinks to experience alcohol‐related effects (i.e., had a lower LR to alcohol). The LR group differences remained significant after covarying for recent drinking quantities. Conclusions: The results confirm that alcohol intake is associated with acute increases in CBF, particularly in frontal regions. Less intense CBF changes were seen in subjects with a genetically influenced characteristic, a low LR to alcohol, that relates to the future risk of heavy drinking and alcohol problems.     

Addition of cue exposure to cognitive-behaviour therapy for alcohol misuse: a randomized trial with dysphoric drinkers

AIM: To test whether addition of moderation-orientated cue exposure (CE) or CE after dysphoric mood induction (emotional CE, ECE) improved outcomes above those from cognitive-behaviour therapy alone (CBT) in people who drank when dysphoric. DESIGN: Multi-site randomized controlled trial comparing CBT with CBT + CE and CBT + ECE. SETTING: Out-patient rooms in academic treatment units in Brisbane and Sydney, Australia. PARTICIPANTS: People with alcohol misuse and problems controlling consumption when dysphoric (n = 163). Those with current major depressive episode were excluded. INTERVENTION: Eight weekly 75-minute sessions of individual treatment for alcohol problems were given to all participants, with CBT elements held constant across conditions. From session 2, CBT + CE participants resisted drinking while exposed to alcohol cues, with two priming doses of their preferred beverage being given in some sessions. After an initial CE session, CBT + ECE participants recalled negative experiences before undertaking CE, to provide exposure to emotional cues of personal relevance. MEASUREMENTS: Alcohol consumption, related problems, alcohol expectancies, self-efficacy and depression. RESULTS: Average improvements were highly significant across conditions, with acceptable maintenance of effects over 12 months. Both treatment retention and effects on alcohol consumption were progressively weaker in CBT + CE and CBT + ECE than in CBT alone. Changes in alcohol dependence and depression did not differ across conditions. CONCLUSIONS: These data do not indicate that addition of clinic-based CE to standard CBT improves outcomes. A different approach to the management of craving may be required.     

The effect of tryptophan depletion on alcohol self-administration in non-treatment-seeking alcoholic individuals

BACKGROUND: Alcohol self-administration in the laboratory has been used to evaluate pharmacological treatments and neurobiological mechanisms that underlie alcohol use in alcohol-dependent individuals. This study evaluated whether attenuation of serotonin synthesis via depletion of its precursor tryptophan reduces the amount of alcohol consumed in a self-administration paradigm in non-treatment-seeking individuals with alcohol use disorders. METHODS: Individuals with alcohol dependence (n = 8) and alcohol abuse (n = 4) who were not seeking treatment were recruited by advertisement and participated in two test days, 1 week apart. Each test session was preceded by administration of a concentrated amino acid drink that resulted in a rapid and significant decline in plasma free tryptophan (active depletion) or a similar drink containing tryptophan (placebo depletion). Tests were conducted in a randomized, double-blind fashion. The test session began with a cue exposure session where subjects were exposed to their favorite alcoholic beverage and asked to rate their craving for alcohol. After this, subjects were administered a priming drink designed to raise blood alcohol levels to 0.02 g%. Subjects then had the opportunity to drink up to eight additional drinks, each designed to raise blood alcohol levels by 0.02 g%, or to receive $3 for each drink not consumed over a 2-hr period. RESULTS: There were no significant differences in alcohol consumed or subjective intoxication with active tryptophan depletion compared with placebo. Self-reported craving correlated with the amount of alcohol consumed in the session. CONCLUSIONS: These data question the dependence of alcohol self-administration on the ongoing synthesis of serotonin.     

Effects of alcohol,personality, and provocation on the expression of anger in men: a facial coding analysis

BACKGROUND: Research has demonstrated that alcohol-related aggression is modulated by anger-based personality traits. However, it is unclear how anger, as a concomitant of aggression, is affected by an interaction among these variables. The present study evaluated the effects of alcohol, anger-based traits, and physical provocation on anger. METHODS: Participants were 136 male social drinkers who completed measures designed to assess trait anger and anger expression styles and were assigned to an alcohol or no-alcohol control beverage group. Participants engaged in a competitive reaction time task in which electric shocks were received from a fictitious opponent. Participants' experience of anger was assessed unobtrusively via the Facial Action Coding System. RESULTS: Intoxicated participants displayed more facial expressions of anger than sober participants. Interactive effects between anger expression styles and beverage group also were detected in that, among intoxicated participants, a positive relationship between facial expressions of anger and the tendency to express anger outwardly was found after high, but not low, provocation. This relationship was not observed at either provocation level in the no-alcohol control group. Similarly, whereas participants' tendency to control anger resulted in fewer facial expressions of anger by intoxicated participants, no such relationship was found among sober participants. CONCLUSIONS: Findings suggest that alcohol intoxication facilitates the experience of anger after provocation and enhances the relationship between state anger and behavioral tendencies to control anger expression.     

Impact of a Structural Intervention to Address Alcohol Use Among Gay Bar Patrons in San Francisco: The PACE Study

We evaluated the impact on alcohol intake and blood alcohol concentration (BAC) of a multi-level structural intervention to increase the availability of free water, coupled with messaging on pacing alcohol intake and normative feedback of blood alcohol concentration in a convenience sample of gay bars in San Francisco. Participants (n = 1,293) were recruited among exiting patrons of four gay bars (two intervention bars and two control bars). Participants were surveyed on alcohol intake and BAC was measured by breathalyzer. Prior to the intervention there were no significant differences in baseline alcohol measures between intervention and control bars. Post-intervention there were significant differences on objective and subjective measures of alcohol consumption: 30% of intervention bar participants had BAC% levels over the legal driving limit (0.08%) compared to 43% of control bar participants, p < 0.0001 and 78% of intervention bar participants were above the AUDIT-C cut-off for hazardous drinking compared to 87% in control bars, p < 0.001.