Rate of alcohol consumption in the daily life of adolescents and emerging adults

Contextual and psychosocial factors influencing drug reward in humans: The importance of non-drug reinforcement

The reinforcing efficacy, or behavior-strengthening effect, of a substance is a critical determinant of substance use typically quantified by measuring behavioral allocation to the substance under schedules of reinforcement with escalating response requirements. Although responses on these tasks are often used to indicate stable reinforcing effects or trait-level abuse potential for an individual, task designs often demonstrate within-person variability across varying degrees of a constraint within experimental procedures. As a result, quantifying behavioral allocation is an effective approach for measuring the impact of contextual and psychosocial factors on substance reward. We review studies using laboratory self-administration, behavioral economic purchase tasks, and ambulatory assessments to quantify the impact of various contextual and psychosocial factors on behavioral allocation toward consumption of a substance. We selected these assessment approaches because they cover the translational spectrum from experimental control to ecological relevance, with consistent support across these approaches representing greater confidence in the effect. Conceptually, we organized factors that influence substance value into two broad categories: factors that influence the cost/benefit ratio of the substance (social context, stress and affect, cue exposure), and factors that influence the cost/benefit ratio of an alternative (alternative non-drug reinforcers, alternative drug reinforcers, and opportunity costs). We conclude with an overview of future research directions and considerations for clinical application.

Trait impulsivity moderates rate of alcohol consumption in daily life

INTRODUCTION

Rate of alcohol consumption, the speed with which people drink, has been linked to a range of outcomes, including alcohol use disorder symptoms and increased positive affect. However, minimal work has identified who is most likely to drink at elevated rates. Impulsivity is associated with increased attention to positive reinforcers specifically (e.g., positive affect). We therefore examined whether people higher in trait impulsivity engage in faster consumption during drinking episodes.

METHODS

Participants were current drinkers (N = 113; 54 people with borderline personality disorder [BPD], a disorder that involves elevated impulsivity, and 59 community people) who completed a 21-day ecological momentary assessment (EMA) protocol. Multilevel models of drinking episodes (Nobservations = 3,444) examined whether self-reported trait impulsivity, measured at baseline, was associated with faster rise in estimated blood alcohol concentration (eBAC) at each follow-up period.

RESULTS

All UPPS sub-scales were associated with faster rise in eBAC across a drinking episode. In a multivariate model including all sub-scales as simultaneous predictors, sensation seeking and (lack of) perseverance were independently positively associated with rate of consumption. Additional analyses indicated that greater negative urgency and sensation seeking were associated with faster rises in eBAC in participants with BPD, relative to community comparisons.

CONCLUSION

In a sample that captured a wide spectrum of impulsivity, greater impulsivity was associated with drinking alcohol at a faster rate. People higher in sensation seeking and (lack of) perseverance may be prone to drink at faster rates out of a desire to maximize the hedonic effects of alcohol.

PUBLIC SIGNIFICANCE STATEMENT

This study finds that people who are more impulsive tend to drink alcohol faster, putting them at greater risk for negative consequences. This may explain, in part, why impulsivity is linked to experiencing alcohol-related problems.

Neuron enriched extracellular vesicles' MicroRNA expression profiles as a marker of early life alcohol consumption

Alcohol consumption may impact and shape brain development through perturbed biological pathways and impaired molecular functions. We investigated the relationship between alcohol consumption rates and neuron-enriched extracellular vesicles' (EVs') microRNA (miRNA) expression to better understand the impact of alcohol use on early life brain biology. Neuron-enriched EVs' miRNA expression was measured from plasma samples collected from young people using a commercially available microarray platform while alcohol consumption was measured using the Alcohol Use Disorders Identification Test. Linear regression and network analyses were used to identify significantly differentially expressed miRNAs and to characterize the implicated biological pathways, respectively. Compared to alcohol naïve controls, young people reporting high alcohol consumption exhibited significantly higher expression of three neuron-enriched EVs' miRNAs including miR-30a-5p, miR-194-5p, and miR-339-3p, although only miR-30a-5p and miR-194-5p survived multiple test correction. The miRNA-miRNA interaction network inferred by a network inference algorithm did not detect any differentially expressed miRNAs with a high cutoff on edge scores. However, when the cutoff of the algorithm was reduced, five miRNAs were identified as interacting with miR-194-5p and miR-30a-5p. These seven miRNAs were associated with 25 biological functions; miR-194-5p was the most highly connected node and was highly correlated with the other miRNAs in this cluster. Our observed association between neuron-enriched EVs' miRNAs and alcohol consumption concurs with results from experimental animal models of alcohol use and suggests that high rates of alcohol consumption during the adolescent/young adult years may impact brain functioning and development by modulating miRNA expression.

Neuron Enriched Exosomal MicroRNA Expression Profiles as a Marker of Early Life Alcohol Consumption

Background

Alcohol consumption may impact and shape brain development through perturbed biological pathways and impaired molecular functions. We investigated the relationship between alcohol consumption rates and neuron-enriched exosomal microRNA (miRNA) expression to better understand the impact of alcohol use on early life brain biology.

Methods

Neuron-enriched exosomal miRNA expression was measured from plasma samples collected from young people using a commercially available microarray platform while alcohol consumption was measured using the Alcohol Use Disorders Identification Test. Linear regression and network analyses were used to identify significantly differentially expressed miRNAs and to characterize the implicated biological pathways, respectively.

Results

Compared to alcohol naïve controls, young people reporting high alcohol consumption exhibited significantly higher expression of four neuron-enriched exosomal miRNAs including miR-30a-5p, miR-194-5p, and miR-339-3p, although only miR-30a-5p and miR-194-5p survived multiple test correction. The miRNA-miRNA interaction network inferred by a network inference algorithm did not detect any differentially expressed miRNAs with a high cutoff on edge scores. However, when the cutoff of the algorithm was reduced, five miRNAs were identified as interacting with miR-194-5p and miR-30a-5p. These seven miRNAs were associated with 25 biological functions; miR-194-5p was the most highly connected node and was highly correlated with the other miRNAs in this cluster.

Conclusions

Our observed association between neuron-enriched exosomal miRNAs and alcohol consumption concurs with results from experimental animal models of alcohol use and suggests that high rates of alcohol consumption during the adolescent/young adult years may impact brain functioning and development by modulating miRNA expression.

Peer-elicited alcohol craving in adolescents and emerging adults: Bridging the laboratory and natural environment

BACKGROUND

Although peers figure prominently in developmental models of alcohol use, our understanding of the influence of peer social context in cue reactivity paradigms with adolescents and emerging adults in the human laboratory and the natural environment is limited. This study tested associations between alcohol craving among youth in the human laboratory using alcohol-related images, with and without peers, and in the natural environment using ecological momentary assessment (EMA).

METHODS

Data for this preregistered secondary analysis were collected prior to randomization in two medication trials (N = 115). Participants completed an image cue exposure paradigm at the baseline laboratory session followed by approximately 7 days of EMA.

RESULTS

In the laboratory, model-based mean comparisons from multilevel models (MLMs) showed that all drinking images elicited greater craving than neutral images. No differences were observed across the three image categories containing alcohol. Image category by age interactions demonstrated that, compared to older youth, younger youth displayed lower craving in response to neutral versus social drinking context with peers images and older, compared to younger, youth displayed higher craving in response to nonsocial drinking images versus social drinking contexts with peers images. In the natural environment, craving was greatest when youth were in the presence of alcohol-using peers and alcohol-related cues, regardless of age. Laboratory craving to alcohol images was positively associated with craving in the natural environment.

CONCLUSIONS

For youth, peers are a salient social context associated with increased craving, particularly in the natural environment. Laboratory cue reactivity to alcohol images predicted real-world craving, further supporting the ecological validity of this paradigm in youth.

Protocol for a mobile laboratory study of co-administration of cannabis concentrates with a standard alcohol dose in humans

Cannabis is commonly used among people who drink alcohol, yet evidence on acute effects of co-use is conflicting. Two important variables that may influence the effects of cannabis and alcohol are cannabinoid content (i.e., the ratio of cannabidiol [CBD] and 9-tetrahydrocannabinol [THC]) as well as the order of use (i.e., cannabis before alcohol vs. alcohol before cannabis). Research is mixed regarding the acute imapct of cannabis on alcohol consumption and intoxication, with some studies suggesting additive effects of alcohol and cannabis, and others demonstrating negligible effects of combining these substances. Further complicating this, high-THC-content cannabis concentrates are increasingly popular on the legal-market, but to our knowledge, no studies have explored concentrate and alcohol co-use. In addition to cannabinoid content, order of use may influence intoxication and other acute effects, but is also understudied. Co-use studies typically administer a fixed dose of alcohol before cannabis, and there is a lack of data on the acute effects of cannabis before alcohol. Thus, there is a need for experimental co-use studies exploring the impact of cannabinoid content (particularly of highly potent cannabis concentrates) and order effects on intoxication. This study uses a federally-compliant mobile laboratory procedure to explore the effects of co-administration of legal-market cannabis concentrates with a moderate alcohol dose (.8g/kg) in a sample of community participants who regularly use alcohol and cannabis. The study will also explore alcohol and cannabis order effects (cannabis before alcohol vs. alcohol before cannabis). Outcomes are objective intoxication (measured using blood cannabinoid level, heart rate, psychomotor performance and breath alcohol level [BrAC]) and subjective intoxication (assessed via self-report measures). Overall, this study may influence harm-reduction recommendations for individuals who drink alcohol and use cannabis.

A critical review of front-loading: A maladaptive drinking pattern driven by alcohol's rewarding effects

Front-loading is a drinking pattern in which alcohol intake is skewed toward the onset of reward access. This phenomenon has been reported across several different alcohol self-administration protocols in a wide variety of species, including humans. The hypothesis of the current review is that front-loading emerges in response to the rewarding effects of alcohol and can be used to measure the motivation to consume alcohol. Alternative or additional hypotheses that we consider and contrast with the main hypothesis are that: (1) front-loading is directed at overcoming behavioral and/or metabolic tolerance and (2) front-loading is driven by negative reinforcement. Evidence for each of these explanations is reviewed. We also consider how front-loading has been evaluated statistically in previous research and make recommendations for defining this intake pattern in future studies. Because front-loading may predict long-term maladaptive alcohol drinking patterns leading to the development of alcohol use disorder (AUD), several future directions are proposed to elucidate the relationship between front-loading and AUD.

The development, but not expression, of alcohol front-loading in C57BL/6J mice maintained on LabDiet 5001 is abolished by maintenance on Teklad 2920x rodent diet

BACKGROUND

Excessive alcohol (ethanol) consumption, such as binge drinking, is extremely commonplace and represents a major health concern. Through modeling excessive drinking in rodents, we are beginning to uncover the neurobiological and neurobehavioral causes and consequences of this pattern of ethanol intake. One important factor for modeling binge drinking in mice is that they reliably drink to blood ethanol concentrations (BECs) of 80 mg/dl or higher. Drinking-in-the-dark (DID) is a commonly used mouse model of binge drinking, and we have shown that this method reliably results in robust ethanol front-loading and binge-level BECs in C57BL/6J (B6) mice and other ethanol-preferring mouse strains/lines. However, establishing the DID model in a new vivarium space forced us to consider the use of rodent diet formulations that we had not previously used.

METHODS

The current set of experiments were designed to investigate the role of two standard rodent diet formulations on binge drinking and the development of ethanol front-loading using DID.

RESULTS

We found that BECs in animals maintained on LabDiet 5001 (LD01) were double those found in mice maintained on Teklad 2920x (TL20). Interestingly, this effect was paralleled by differences in the degree of front-loading, such that LD01-fed mice consumed approximately twice as much ethanol in the first 15 min of the 2-h DID sessions as the TL20-fed mice. Surprisingly, however, mice that developed front-loading during maintenance on the LD01 diet continued to display front-loading behavior after being switched to the TL20 diet.

CONCLUSIONS

These data emphasize the importance of choosing and reporting diet formulations when conducting voluntary drinking studies and support the need for further investigation into the mechanisms behind diet-induced differences in binge drinking, particularly front-loading.

Naltrexone moderates the association of alcohol use and affect among adolescent drinkers in daily life

BACKGROUND

Naltrexone is an efficacious medication for the treatment of alcohol use disorder in adults. As an opioid receptor antagonist, naltrexone blocks activation of the endogenous opioid system, which is involved in the affectively reinforcing properties of substance use. Few studies, however, have examined the moderating effect of naltrexone on the association between affect and alcohol use. Additionally, most existing research on naltrexone has been with adults in the human laboratory.

METHOD

We conducted a secondary analysis of ecological momentary assessment data from a randomized, double-blinded, placebo-controlled cross-over study that compared naltrexone (50 mg/daily) and placebo in 26 adolescents (15 to 19 years old) who exhibited problematic drinking patterns. Multilevel models tested whether naltrexone moderated associations of alcohol use with both positive and negative affect (PA, NA).

RESULTS

Results indicated that, during naltrexone treatment, greater estimated blood alcohol concentration (eBAC) levels were associated with greater NA further into drinking episodes. In turn, greater NA after the first drink of an episode was associated with reduced subsequent eBAC values during naltrexone treatment. Low PA was also associated with lower subsequent eBAC levels in the naltrexone condition after the first drink.

CONCLUSIONS

These findings support the idea that naltrexone can disrupt the association between affect and alcohol use, effects that emerge later in drinking episodes. Greater attention to the effects of naltrexone on affect and reinforcement may help to tailor psychotherapy to maximize the benefits of naltrexone. However, in the present study, as most drink reports were in the first 2 h of the drinking episode and participants reported affect only at the first three end-drink reports of a drinking episode (limiting the number of drinks reported), we had reduced power to detect effects in the continuation phase. Thus, replication of the findings is needed using a design that assesses the impact of naltrexone across the entire episode.

Perceived friendship and binge drinking in young adults: A study of the Human Connectome Project data

BACKGROUND

Peer influences figure prominently in young adult binge drinking. Women have trended to show a level of alcohol use on par with men during the last decades. It would be of interest to investigate the neural processes of social cognition that may underlie binge drinking and the potential sex differences.

METHODS

Here, we examined the data of the Human Connectome Project where we identified a total of 175 binge drinkers (125 men) and 285 non-binge drinkers (97 men) performing a social cognition task during brain imaging. We analyzed the imaging data with published routines and evaluated the results at a corrected threshold.

RESULTS

Both male and female binge relative to non-binge drinkers showed higher perceived friendship. Binge relative to non-binge drinkers demonstrated diminished activations in the anterior medial orbitofrontal cortex (amOFC) during perception of social vs. random interaction, with a more prominent effect size in women. Further, whole-brain regression identified activity of the right posterior insula (rPI) in negative correlation with perceived friendship score in non-binge drinking women. Post-hoc analyses showed significant correlation of rPI activity with perceived friendship, amOFC activity, and a summary measure of alcohol use severity identified by principal component analysis, across all subjects. Mediation and path analysis demonstrated a significant model: amOFC activity → rPI activity → perceived friendship → severity of alcohol use.

CONCLUSIONS

These findings support peer influences on binge drinking and suggest neural correlates that may relate altered social cognitive processing to alcohol misuse in young adults.

What We Talk About When We Talk About Binge Drinking: Towards an Integrated Conceptualization and Evaluation

RATIONALE

Binge drinking (BD), characterized by recurring alternations between intense intoxication episodes and abstinence periods, is the most frequent alcohol consumption pattern in youth and is growing in prevalence among older adults. Many studies have underlined the specific harmful impact of this habit by showing impaired abilities in a wide range of cognitive functions among binge drinkers, as well as modifications of brain structure and function.

AIMS

Several controversies and inconsistencies currently hamper the harmonious development of the field and the recognition of BD as a specific alcohol consumption pattern. The main concern is the absence of consensual BD conceptualization, leading to variability in experimental group selection and alcohol consumption evaluation. The present paper aims at overcoming this key issue through a two-step approach.

METHODS AND CONCLUSIONS

First, a literature review allows proposing an integrated BD conceptualization, distinguishing it from other subclinical alcohol consumption patterns. Six specific characteristics of BD are identified, namely, (1) the presence of physiological symptoms related to BD episodes, (2) the presence of psychological symptoms related to BD episodes, (3) the ratio of BD episodes compared to all alcohol drinking occasions, (4) the frequency of BD episodes, (5) the consumption speed and (6) the alternation between BD episodes and soberness periods. Second, capitalizing on this conceptual clarification, we propose an evaluation protocol jointly measuring these six BD characteristics. Finally, several research perspectives are presented to refine the proposed conceptualization.

Alcohol subjective responses in heavy drinkers: Measuring acute effects in the natural environment versus the controlled laboratory setting

BACKGROUND

For decades, laboratory alcohol challenges have been the "gold standard" for measuring individual differences in alcohol's subjective effects. However, these approaches are expensive and labor-intensive, making them impractical for large-scale use. This study examined the reliability and validity of a new high-resolution EMA (HR-EMA) ambulatory approach to assessing alcohol use and subjective responses in drinkers' natural environments.

METHODS

Participants were 83 young adult heavy social drinkers (58% male; mean ± SD age = 25.4 ± 2.6 years) who completed up to two smartphone-based, 3-h HR-EMA assessments of alcohol use and related subjective responses in their typical drinking environments. Reported alcohol consumption during the HR-EMA periods was used to calculate estimated blood alcohol concentration (eBAC). Subjective effects were measured using the Brief Biphasic Alcohol Effects Scale (B-BAES) and Drug Effects Questionnaire (DEQ). All participants also completed identical measures during a separate, 4 to 5-h laboratory session in which they received a 0.8 g/kg alcohol challenge.

RESULTS

Most natural environment drinking episodes (87%) met or exceeded the threshold for binge drinking (final mean eBAC = 0.12 g/dl). Associations between reported alcohol use and subjective responses on the B-BAES and DEQ were strongest earlier in the drinking events, with fair reliability of reported subjective effects across two HR-EMA episodes (intraclass correlation [ICC] range = 0.46-0.49). There was fair-to-good correspondence between HR-EMA- and laboratory-derived subjective responses (ICC range = 0.49-0.74), even after accounting for differences in alcohol consumption and drinking context. Reported stimulating and rewarding alcohol effects were higher in the ambulatory than laboratory setting, and vice versa for sedating effects.

CONCLUSIONS

This study supports the reliability and validity of smartphone-based HR-EMA to measure alcohol use and subjective responses in heavy drinkers' natural environments. These findings lend support to the use of ambulatory HR-EMA as a measure of alcohol subjective responses in risky drinkers when a laboratory protocol is not practical, feasible, or safe.

How much and how fast: Alcohol consumption patterns, drinking-episode affect, and next-day consequences in the daily life of underage heavy drinkers

BACKGROUND

Understanding how alcohol consumption patterns are associated with negative and positive outcomes can inform efforts to reduce negative consequences through modification of those patterns. This is important in underage drinkers, many of whom drink heavily despite negative consequences. Most work has focused on the amount of alcohol consumed, but amount provides limited information about consumption patterns compared to rate of consumption, or how fast individuals drink. We therefore examined associations of both amount and rate of consumption with negative and positive outcomes (immediate affective states and next-morning consequences) in daily life.

METHOD

Ninety-five college students aged 18-20 years completed ecological momentary assessment over 28 days. Participants reported number of standard drinks consumed and positive and negative affect hourly within drinking episodes. Estimated blood alcohol concentration (eBAC) values were used to create amount and rate of consumption indicators. Each morning after drinking, participants reported negative (e.g., blackout, hangover) and positive (e.g., new friend, making others laugh) consequences.

RESULTS

Within drinking episodes, multilevel models showed faster consumption was associated with reduced negative affect and both larger amount and faster consumption were associated with greater positive affect. Further, amount and rate were both associated with greater likelihood of a negative consequence the next morning. Rate, but not amount, was associated with more positive consequences.

CONCLUSIONS

Not only how much but also how fast individuals drink may be important for the positive and negative outcomes they experience. Interventions to reduce negative alcohol-related outcomes should consider not only amount, but also rate of consumption.

High Alcohol-Preferring Mice Show Reaction to Loss of Ethanol Reward Following Repeated Binge Drinking

BACKGROUND

Beyond yielding high blood ethanol (EtOH) concentrations (BECs), binge-drinking models allow examination of drinking patterns which may be associated with EtOH's rewarding effects, including front-loading and consummatory successive negative contrast (cSNC), a decrease in intake when only water is available to subjects expecting EtOH. The goals of the current study were to broaden our understanding of these reward-related behaviors during binge EtOH access in high alcohol-preferring (HAP) replicate lines (HAP2 and HAP3) of mice selectively bred to prefer alcohol. We hypothesized that both lines would show evidence of front-loading during binge EtOH access and that we would find a cSNC effect in groups where EtOH was replaced with water, as these results have been shown previously in HAP1 mice.

METHODS

HAP replicate 2 and replicate 3 female and male mice were given 2 hours of EtOH or water access in the home cage for 15 consecutive days using "drinking in the dark" (DID) procedures. Mice received the same fluid (either 20% unsweetened EtOH or water) for the first 14 days. However, on the 15th day, half of the mice from these 2 groups were provided with the opposite assigned fluid (EtOH groups received water and vice versa). Intake was measured in 1-minute bins using specialized sipper tubes, which allowed within-session analyses of binge-drinking patterns.

RESULTS

EtOH front-loading was observed in both replicates. HAP3 mice displayed front-loading on the first day of EtOH access, whereas front-loading developed following alcohol experience in HAP2 mice, which may suggest differences in initial sensitivity to EtOH reward. Consummatory SNC, which manifests as lower water intake in mice expecting EtOH as compared to mice expecting water, was observed in both replicates.

CONCLUSIONS

These findings increase confidence that defined changes in home cage consummatory behavior are driven by the incentive value of EtOH. The presence of cSNC across HAP replicates indicates that this reaction to loss of reward is genetically mediated, which suggests that there is a biological mechanism that might be targeted.