Clinical significance of alcohol intake parameters at initiation of drinking

Intermittent voluntary ethanol consumption combined with ethanol vapor exposure during adolescence increases drinking and alters other behaviors in adulthood in female and male rats

Epidemiological studies suggest that binge drinking is prevalent among adolescents, and may result in neurobehavioral consequences. Animal models provide the experimental control to investigate the consequences of "binge" alcohol exposure during this neurodevelopmental epoch. The current study used an animal model that combined an intermittent pattern of alcohol vapor exposure with voluntary drinking of 20% unsweetened alcohol in adolescent male and female Wistar rats (postnatal day [PD] 22-62), in order to test for potential differences in behavioral changes, ethanol drinking, and hypocretin/orexin (Hcrt/OX) signaling associated with exposure status. Two weeks after discontinuation of the alcohol vapor exposure and drinking during adolescence, rats were tested in adulthood for anxiety-like behaviors using a modified open-field conflict task, pre-pulse facilitation of startle response, light/dark box, and marble burying test. Adolescent alcohol exposure led to overall decreased startle response and increased behavioral arousal in the light/dark chamber during adulthood. Additionally, male rats demonstrated more disinhibited behavior during the conflict task compared to females, and female rats exhibited more rearing behavior during the light/dark test. Rats were also given a 2-bottle choice test that resulted in adolescent alcohol-exposed rats drinking significantly more alcohol in adulthood. Further, female rats also consumed more alcohol in adulthood compared to males. Estrous cycle phase did not account for any of the sex differences observed in the behavioral measures. Histological results indicated that adolescent alcohol did not alter Hcrt/OX-1 or Hcrt/OX-2 receptor mRNA expression levels in adult rats compared to control adults. However, female rats expressed a higher level of Hcrt/OX-1 and Hcrt/OX-2 receptor mRNA in the frontal cortex compared to males. These data suggest that our current model of intermittent ethanol exposure in adolescence can modestly affect both behavior and future consumption of alcohol and that Hcrt/OX receptor signaling differs between males and females.

Environmental enrichment enhances conditioned place preference to ethanol via an oxytocinergic-dependent mechanism in male mice

Environmental conditions, such as stress and environmental enrichment (EE), influence predisposition to alcohol use/abuse; however, the underlying mechanisms remain unknown. To assess the effect of environmental conditions on the initial rewarding effects of alcohol, we examined conditioned place-preference (CPP) to alcohol following exposure to EE in mice. Since social context is a major factor contributing to initial alcohol-drinking, we also assessed the impact of EE on the levels of the "social neuropeptide" oxytocin (OT) and its receptor, OTR. Finally, we assessed the effect of pharmacological manipulations of the oxytocinergic system on EE-induced alcohol CPP. While EE increased sociability and reduced anxiety-like behaviors, it caused a ∼3.5-fold increase in alcohol reward compared to controls. EE triggered profound neuroadaptations of the oxytocinergic system; it increased hypothalamic OT levels and decreased OTR binding in the prefrontal cortex and olfactory nuclei of the brain. Repeated administration of the OT analogue carbetocin (6.4 mg/kg/day) mimicked the behavioral effects of EE on ethanol CPP and induced similar brain region-specific alterations of OTR binding as those observed following EE. Conversely, repeated administration of the OTR antagonist L,369-899 (5 mg/kg/day) during EE exposure, but not during the acquisition of alcohol CPP, reversed the pronounced EE-induced ethanol rewarding effect. These results demonstrate for the first time, a stimulatory effect of environmental enrichment exposure on alcohol reward via an oxytocinergic-dependent mechanism, which may predispose to alcohol abuse. This study offers a unique prospective on the neurobiological understanding of the initial stages of alcohol use/misuse driven by complex environmental-social interplay.

Age of Drinking Initiation as a Risk Factor for Alcohol Use Disorder Symptoms is Moderated by ALDH2*2 and Ethnicity

BACKGROUND

An early age of drinking initiation (ADI) has been associated with increased risk for alcohol use disorders (AUDs), but the consistency of this risk across diverse samples has not been well studied. The purpose of this study was to examine whether the pathway from ADI to AUD symptoms by early adulthood is moderated by ethnicity and possessing an alcohol-metabolizing gene ALDH2*2 variant allele.

METHODS

We used multigroup structural equation modeling, including 5 groups split by ethnicity and ALDH2*2, to examine the consistency of the path from ADI to AUD symptoms in 604 Chinese-, Korean-, and White-American college students. We further examined the effects of ALDH2*2, ethnicity, and their interaction in Asians to better understand their unique contributions to the moderation.

RESULTS

The association between ADI and AUD symptoms was moderated, with ADI negatively associated with AUD symptoms among Koreans without ALDH2*2 and Whites, but not among Koreans with ALDH2*2 or Chinese regardless of ALDH2*2. Both ALDH2*2 and ethnicity within Asians contributed unique variability in the effect.

CONCLUSIONS

Ethnicity and ALDH2*2 altered the relationship of ADI as a risk factor for AUD symptoms. Being Chinese and possessing an ALDH2*2 allele within Koreans both buffered against the risk for AUD symptoms associated with earlier ADI, indicating that this relationship can be attenuated by protective factors.

Alcohol drinking during adolescence increases consumptive responses to alcohol in adulthood in Wistar rats

Binge drinking and the onset of alcohol-use disorders usually peak during the transition between late adolescence and early adulthood, and early adolescent onset of alcohol consumption has been demonstrated to increase the risk for alcohol dependence in adulthood. In the present study, we describe an animal model of early adolescent alcohol consumption where animals drink unsweetened and unflavored ethanol in high concentrations (20%). Using this model, we investigated the influence of drinking on alcohol-related appetitive behavior and alcohol consumption levels in early adulthood. Further, we also sought to investigate whether differences in alcohol-related drinking behaviors were specific to exposure in adolescence versus exposure in adulthood. Male Wistar rats were given a 2-bottle choice between 20% ethanol and water in one group and between two water bottles in another group during their adolescence (Postnatal Day [PD] 26-59) to model voluntary drinking in adolescent humans. As young adults (PD85), rats were trained in a paradigm that provided free access to 20% alcohol for 25 min after completing up to a fixed-ratio (FR) 16 lever press response. A set of young adult male Wistar rats was exposed to the same paradigm using the same time course, beginning at PD92. The results indicate that adolescent exposure to alcohol increased consumption of alcohol in adulthood. Furthermore, when investigating differences between adolescent high and low drinkers in adulthood, high consumers continued to drink more alcohol, had fewer FR failures, and faster completion of FR schedules in adulthood, whereas the low consumers were no different from controls. Rats exposed to ethanol in young adulthood also increased future intake, but there were no differences in any other components of drinking behavior. Both adolescent- and adult-exposed rats did not exhibit an increase in lever pressing during the appetitive challenge session. These data indicate that adolescent and early adult alcohol exposure can increase consumptive aspects of drinking but that adolescent exposure may preferentially influence the motivation to drink.

Associations between a history of binge drinking during adolescence and self-reported responses to alcohol in young adult Native and Mexican Americans

BACKGROUND

Binge drinking during adolescence is common and may predict increased drinking in young adulthood and enhanced risk of alcohol dependence. Variation in level of response to the hedonic and adverse effects of alcohol is in part an inherited factor that may also influence its use, abuse, and dependence. This study investigated, in young adults, whether an association could be demonstrated between variation in self-reported responses to alcohol and a history of binge drinking during adolescence.

METHODS

Young adult (18 to 30 years, n = 790) Native Americans and Mexican Americans were recruited from the community and completed a structured diagnostic interview. Response to alcohol was indexed using the expectation version of the Subjective High Assessment Scale (SHAS-E). An adolescent history of regular binge drinking was defined as drinking 5 or more drinks for boys and 4 or more drinks for girls per drinking occasion at least once a month during their highest drinking period prior to the age of 18.

RESULTS

An adolescent history of regular binge drinking was found to be associated with a lower level of self-reported responses to the negative aspects of alcohol intoxication (feeling terrible) as well as to the overall level of intoxication, but not to the positive impressions of intoxication (feeling great) on the SHAS-E. A history of regular adolescent binge drinking was also correlated with less feelings of the "terrible" and "total" effects of alcohol, as indexed by the SHAS-E, in a linear regression model that included several diagnostic and demographic variables such as a history of conduct disorder and current levels of drinking.

CONCLUSIONS

These data suggest that a history of adolescent binge drinking is associated with a reduction in the self-reported level of intoxication in young adulthood, a factor that could theoretically lead to increased risk of alcohol dependence.

Effects of adolescent onset voluntary drinking followed by ethanol vapor exposure on subsequent ethanol consumption during protracted withdrawal in adult Wistar rats

Epidemiological studies have demonstrated that heavy drinking and alcohol abuse and dependence peak during the transition between late adolescence and early adulthood. The objective of the present study was to determine whether a model of early onset adolescent ethanol drinking exposure that is followed by an ethanol vapor regimen during late adolescence and young adulthood leads to an increase in drinking in adulthood. In this model, initiation of voluntary ethanol drinking in adolescence, using a sweetened solution, was followed by an 8-wk intermittent ethanol vapor regimen in Wistar rats. A limited-access two-bottle choice paradigm was then used to measure intake of a 10% (w/v) ethanol solution. No differences in water intake (g/kg), total fluid intake (ml/kg) and body weight (g) were observed between air-exposed and ethanol-vapor exposed groups during the pre-vapor and post-vapor phases. The 8 weeks of ethanol vapor exposure was found to produce only a modest, but statistically significant, elevation of ethanol intake during the protracted withdrawal period, compared to air-exposed rats. A significant increase in ethanol preference ratio was also observed in ethanol-vapor exposed rats during the sucrose-fading phase, but not during the protracted withdrawal period. The findings from the present study suggest that in addition to alcohol exposure, environmental variables that impact appetitive as well as consumptive behaviors may be important in developing robust drinking effects that model, in animals, the increased risk for alcohol dependence seen in some human adolescents who begin drinking at an early age.

Age at regular drinking, clinical course, and heritability of alcohol dependence in the San Francisco family study: a gender analysis

We examined gender differences in age of onset, clinical course, and heritability of alcohol dependence in 2,524 adults participating in the University of California San Francisco (UCSF) family study of alcoholism. Men were significantly more likely than women to have initiated regular drinking during adolescence. Onset of regular drinking was not found to be heritable but was found to be significantly associated with a shorter time to onset of alcohol dependence. A high degree of similarity in the sequence of alcohol-related life events was found between men and women, however, men experienced alcohol dependence symptoms at a younger age and women had a more rapid clinical course. Women were found to have a higher heritability estimate for alcohol dependence (h(2)= .46) than men (h(2)= .32). These findings suggest that environmental factors influencing the initiation of regular drinking rather than genetic factors associated with dependence may in part underlie some of the gender differences seen in the prevalence of alcohol dependence in this population. (Am J Addict 2010;00:1-10).

The association between earlier age of first drink, disinhibited personality, and externalizing psychopathology in young adults

Earlier age of first drink (AFD) of alcohol is associated with higher rates of alcohol abuse and dependence as well as a range of other externalizing problems. This study tested the hypotheses that in young adults earlier AFD is associated with [1] the common variance among externalizing problems (lifetime alcohol, marijuana, other drug, childhood conduct, and adult antisocial behavior problems) rather than being uniquely associated with alcohol problems, and [2] the disinhibited personality traits of social deviance and impulsivity, and that the association between earlier AFD and externalizing problems is partly accounted for by disinhibited personality. The sample (N=502) included 299 young adults with a history of alcohol dependence (AD) and 203 subjects with no history of AD. Analyses showed that [1] earlier AFD was associated with the covariance among the different domains of externalizing problems and was not unique to any one externalizing problem, [2] earlier AFD was associated with social deviance and impulsivity, and [3] social deviance and impulsivity accounted for part of the association between earlier AFD and externalizing problems. The results suggest that earlier AFD is associated with a vulnerability to disinhibitory disorders and is not specifically associated with alcohol problems.

Cannabis dependence in the San Francisco Family Study: age of onset of use, DSM-IV symptoms, withdrawal, and heritability

Cannabis is the most widely used illicit drug in the United States, yet the role of genetics in individual symptoms associated with cannabis use disorders has not been evaluated. The purpose of the present set of analyses was to describe the symptomatology and estimate the heritability of DSM-IV criteria/symptoms of cannabis dependence in a large sample of families. Participants were 2524 adults, participating in the University of California San Francisco (UCSF) Family Study of alcoholism. Seventy percent of the sample had ever used cannabis and 13.9% met DSM-IV criteria for cannabis dependence. Younger age at first cannabis use was found to be significantly associated with a shortened survival to becoming cannabis dependent. Although a greater percentage of men met criteria for cannabis dependence, women were found to demonstrate "telescoping" as indexed by a shorter survival time from initial use to dependence as compared to men. A cannabis withdrawal syndrome was identified in users, the primary symptoms of which were nervousness, appetite change, and sleep disturbance. Cannabis use (h(2)=0.31) and dependence (h(2)=0.20), age at first use, individual DSM-IV criteria for dependence, and cannabis-use associated symptoms of depression, trouble concentrating and paranoia were all found to be heritable. These findings suggest that within this population that cannabis use and dependence, as well as individual cannabis dependence symptoms have a significant heritable component, that cannabis dependence is more likely to occur when use begins during adolescence, and that the cannabis dependence syndrome includes a number of heritable untoward psychiatric side effects including withdrawal.

Externalizing disorders in American Indians: comorbidity and a genome wide linkage analysis

Alcohol dependence is one of the leading causes of morbidity and mortality in Native Americans. Externalizing disorders such as conduct disorder (CD) and antisocial personality disorder (ASPD) have been demonstrated to have significant comorbidity with alcohol dependence in the general population. This study's aims were to: assess the comorbidity of DSM-III-R ASPD and CD with alcohol dependence, to map susceptibility loci for ASPD and CD, and to see if there is overlap with loci previously mapped for alcohol dependence phenotypes in 587 American Indians. Alcohol dependence was found to be comorbid with DSM-III-R ASPD but not CD. However, the amount of alcohol dependence in the population attributable to ASPD and/or CD is low. ASPD and the combined phenotype of participants with ASPD or CD were both found to have significant heritability, whereas no significant evidence was found for CD alone. Genotypes were determined for a panel of 791 micro-satellite polymorphisms in 251 of the participants. Analyses of multipoint variance component LOD scores, for ASPD and ASPD/CD, revealed six locations that had a LOD score of 2.0 or above: on chromosome 13 for ASPD and on chromosomes 1, 3, 4, 14, 17, and 20 for ASPD/CD. These results corroborate the importance of several chromosomal regions highlighted in prior segregation studies for externalizing diagnoses. These results also further identify new regions of the genome, that do not overlap with alcohol dependence phenotypes previously identified in this population, that may be unique to either the phenotypes evaluated or this population of American Indians.

Früher Einstieg in den Alkohol- und Tabakkonsum - Indikator für eine erhöhte Suchtgefährdung?

Zusammenfassung: Fragestellung: Der frühzeitige Beginn des Substanzkonsums gilt aufgrund mehrerer US-amerikanischer Studien als einer der besten Prädiktoren späterer Suchtprobleme. In der vorliegenden Untersuchung wird der Einfluss des frühen Einstiegsalters auf das Suchtverhalten in einer Kultur überprüft, die damit vergleichsweise freizügig umgeht und in der Jugendliche daher auch früher mit dem Konsum beginnen und höhere Konsumraten aufweisen. Methodik: In einer prospektiven Längsschnittstudie an einer Geburtskohorte von 384 Risikokindern wurden das Erstkonsumalter für Tabak und Alkohol, das Alter bei Beginn des regelmäßigen Konsums sowie verschiedene Parameter des Alkohol- und Tabakkonsums mit 15 Jahren erhoben. Ergebnisse: Das Konsumverhalten (Häufigkeit und Menge) sowie das Rauschtrinken als spezifisches Konsummuster und erste Symptome von Tabakabhängigkeit können durch das Alter beim Erstkonsum signifikant vorhergesagt werden. Beim Tabakkonsum und bei den weiblichen Jugendlichen ist dieser Zusammenhang generell höher. Schlussfolgerungen: Ein frühes Einstiegsalter stellt auch bei deutschen Jugendlichen einen Risikofaktor für den Alkohol- und Tabakkonsum in einem sehr frühen Stadium dar. Zu prüfen bleibt, ob es sich dabei um einen kausalen oder nichtkausalen Zusammenhang handelt.

Age at First Intoxication and Alcohol Use Disorders in Southwest California Indians

BACKGROUND

In several national surveys, a younger age of onset of first drink and/or regular drinking has been associated with a higher likelihood of the development of alcohol dependence. Some studies have suggested that age at first drink is primarily an environmentally driven variable whereas others suggest that it may be partially mediated by a general vulnerability to exhibit problem behaviors. Although Native Americans, overall, have the highest prevalence of alcohol dependence of any U.S. ethnic group, the relationship of age of onset of intoxication with alcohol dependence in Native American populations is relatively unknown.

METHODS

Demographic information and DSM-III-R diagnoses were obtained from 525 Southwest California (SWC) Indian adults residing on contiguous reservations. Survival analyses and Cox and logistic regression were used to investigate the relationship between age of onset of first intoxication and the development of alcohol dependence. Heritability of the age of onset of first intoxication was also determined using SOLAR.

RESULTS

Age at first intoxication was not found to be heritable in this population. Early onset of intoxication, however, was found to be significantly associated with both a shorter time to onset of alcohol dependence and increased prevalence in this population, even on taking into account several other risk factors including externalizing diagnoses.

CONCLUSIONS

These data suggest that effective environmental prevention efforts at reducing underage drinking may be an important strategy to lower the prevalence of alcohol dependence in this high-risk population.

Influence of age at drinking onset on long-term ethanol self-administration with deprivation and stress phases

BACKGROUND

Onset of alcohol use during adolescence has potentially long-lasting consequences, e.g., prospective alcohol dependence. To obtain new insight into the effects of early chronic ethanol consumption, we compared the drinking behavior of two adult male Wistar rat groups: one that initiated alcohol consumption during adolescence (adolescent group) and the other that initiated their drinking during adulthood (adult group) in a model of long-term alcohol self-administration. We investigated the magnitude of the effects of deprivation and stress on alcohol intake and the influence of these events on the alcohol drinking behavior across time.

METHODS

Heterogeneous Wistar rats aged 31 days (adolescents) and 71 days (adults) were given ad libitum access to water, as well as 5% and 20% ethanol solutions during an observation period of 30 wk. A deprivation phase of 14 days was instituted after eight wk of access to alcohol. After 16 and 26 wk of alcohol access, all animals were subjected for three consecutive days to forced swimming and electric foot shocks, respectively.

RESULTS

At the onset of drinking, adolescent animals consumed less alcohol and showed lower preference than adults. The deprivation phase was followed by increased intake of highly concentrated ethanol solution without appreciable differences between age groups. Repeated swim stress produced a slight increase in ethanol consumption in both animal groups; however, alcohol intake was not significantly different between groups, whereas the foot shock stress-induced increase in alcohol intake was significantly higher in the animal group that initiated alcohol consumption during adolescence. After swim stress, the drinking behavior of the adolescent group resembled that of the adult group. In particular, the adolescent group increased their preference for 20% ethanol solution for the remainder of the experiment.

CONCLUSIONS

Age of voluntary alcohol drinking onset does not appear to be a strong predictor for prospective alcohol intake and relapse-like drinking behavior under the present experimental conditions. However, male Wistar rats that initiated alcohol consumption during adolescence seem to be more susceptible to acute stressor-specific effects in terms of alcohol consumption.

Relationship of Age of First Drink to Child Behavioral Problems and Family Psychopathology

BACKGROUND

Studies have implicated a wide variety of variables as being associated with an early age of first drink (AFD). AFD in turn has been associated with a variety of negative outcomes in adolescence and early adulthood. This study is designed to quantify the contributions of these antecedent variables to prediction of AFD; in particular it will carefully examine the involvement of variables in four areas (child characteristics, family demographics, family psychopathology, and child behavior problems).

METHODS

Using data from a multicenter study on alcoholism, we first investigated the differences between two groups of children (ages 7 to 17 years), one from families heavily loaded for alcohol dependence and the other from population controls. Second, a multidomain, multistep regression model using child characteristics, family demographics, family psychopathology, and child behavior problems was performed to determine significant contributors to predicted AFD.

RESULTS

Five variables initially contributed to the prediction of AFD. These included gender, age at interview, the number of adult sibs with alcohol dependence, being held back a year in school, and conduct scale score. However, the number of conduct symptoms appeared to contain the contributions of gender and being held back a grade in school, and these two variables were subsequent removed from the model. The remaining three variables explained 45% of the model variance; age at interview accounted for 38.3%, conduct scale score accounted for 6.2%, and the number of alcohol-dependent adult sibs accounted for 0.5%. No family history measures of alcohol dependence or antisocial personality disorder were contributory to the prediction model for AFD.

CONCLUSIONS

Both the "number of conduct symptoms" and the "number of adult sibs with alcohol dependence" are inversely associated with predicted AFD. The latter variable appears marginally predictive of AFD and suggests a condition in which the child's household, regardless of strength of family history of AD (or antisocial personality disorder), appears conducive to early drinking. Thus, child and environmental factors are stronger predictors of age of first drink than family history.

Association of age at first drink with current alcohol drinking variables in a national general population sample

BACKGROUND

Age at first drink has been found to be associated with alcohol problems in adulthood, but little is known regarding the relationship of age at first drink and current alcohol intake variables. This study was designed to determine the relationship of age at first drink to traditional drinking variables as well as novel current drinking variables assessed for the first time in a national general population sample.

METHOD

Data on age of first drink, pathological drinking (DSM-IV alcohol abuse or dependence) and alcohol intake on typical drinking occasions were collected on a national general population sample of 2631 subjects by means of computerized telephone interviewing. Variables assessed for the first time in a national survey included the duration of the typical drinking episode and the predicted peak blood alcohol levels achieved during those episodes.

RESULTS

Data from 2276 subjects who reported an age at first drink were used in this study. Men and lifetime pathological drinkers reported an earlier age at first drink than did, respectively, women or lifetime nonpathological drinkers. There were significant regression coefficients between age at first drink and several current drinking measures. The largest coefficients were usually found within younger age groups.

CONCLUSIONS

Age at first drink may be a useful predictive variable for some current drinking measures, including predicted peak blood alcohol levels as well as lifetime alcohol pathology. Further support was provided for the "convergence" hypothesis that the drinking habits of women have become more like those of men.