Alcohol consumption and cognitive functioning in college students

Effects of Emerging Alcohol and Marijuana Use Behaviors on Adolescents' Neuropsychological Functioning Over Four Years

OBJECTIVE

Adolescence is a period of neuromaturation concomitant with increased substance involvement. Most substance use studies of adolescents have focused on categorical classifications (e.g., dependent vs. nondependent), but little is known about the influence of specific substance use behaviors on cognitive functioning in youth.

METHOD

This study prospectively evaluated the quantitative effects of different substance use behaviors on neuropsychological functioning. A cognitive test battery was administered at baseline (ages 12-14 years), before substance use initiation, and at follow-up (M = 4.0 years, SD = 2.0) to evaluate changes in verbal memory, visuospatial ability, psychomotor speed, processing speed, and working memory. Robust regressions examined substance use behaviors as predictors of neuropsychological functioning (N = 234).

RESULTS

Several substance use behaviors predicted follow-up neuropsychological functioning above and beyond effects of baseline performance on the same measure (ps < .05). Specifically, more alcohol use days predicted worse verbal memory (β = -.15) and visuospatial ability (β = -.19). More postdrinking effects (β = -.15) and greater drug use (β = -.11) predicted worse psychomotor speed. Processing speed was not predicted by substance involvement (ps > .05). Unexpectedly, more alcohol use predicted better working memory performance (β = .12).

CONCLUSIONS

The frequency and intensity of adolescent alcohol use may be more intricately linked to neuropsychological outcomes than previously considered. The low prevalence of substance use disorder in the sample suggests that subdiagnostic users may still experience adverse effects to verbal memory, visuospatial functioning, and psychomotor speed after initiating intense or frequent alcohol use.

Moderate alcohol consumption and cognitive risk

We reviewed 143 papers that described the relationship between moderate drinking of alcohol and some aspect of cognition. Two types of papers were found: (1) those that provided ratios of risk between drinkers and nondrinkers (74 papers in total) and (2) those that, although they did not provide such ratios, allowed cognition in drinkers to be rated as "better," "no different," or "worse" than cognition in nondrinkers (69 papers in total). The history of research on moderate drinking and cognition can be divided into two eras: 1977-1997 and 1998-present. Phase I (1977-1997) was the era of neuropsychological evaluation involving mostly young to middle-aged (18-50 years old) subjects. Although initial studies indicated moderate drinking impaired cognition, many later studies failed to confirm this, instead finding no difference in cognition between drinkers and nondrinkers. Phase II (1998-present) was and is the era of mental status exam evaluation involving mostly older (≥55 years old) subjects. These studies overwhelmingly found that moderate drinking either reduced or had no effect on the risk of dementia or cognitive impairment. When all the ratios of risk from all the studies in phase II providing such ratios are entered into a comprehensive meta-analysis, the average ratio of risk for cognitive risk (dementia or cognitive impairment/decline) associated with moderate "social" (not alcoholic) drinking of alcohol is 0.77, with nondrinkers as the reference group. The benefit of moderate drinking applied to all forms of dementia (dementia unspecified, Alzheimer's disease, and vascular dementia) and to cognitive impairment (low test scores), but no significant benefit against cognitive decline (rate of decline in test scores) was found. Both light and moderate drinking provided a similar benefit, but heavy drinking was associated with nonsignificantly higher cognitive risk for dementia and cognitive impairment. Although the meta-analysis also indicated that wine was better than beer or spirits, this was based on a relatively small number of studies because most studies did not distinguish among these different types of alcohol. Furthermore, a number of the studies that did make the distinction reported no difference among the effects of these different types of alcohol. Therefore, at present this question remains unanswered. Analysis also showed that the presence of the apolipoprotein E epsilon 4 allele eliminated the benefit of moderate drinking. However, this was based on a relatively small number of studies and several other studies have found a beneficial effect of the epsilon e4 allele. Further studies are necessary to settle this question. The benefit of moderate alcohol for cognition was seen in both men and women, although the amount and pattern of drinking is very different between the two sexes. Lastly, the finding of unaffected or significantly reduced cognitive risk in light to moderate drinkers was seen in 14/19 countries for which country-specific ratio data were available, with three of the five remaining countries showing nonsignificant reductions as well. Overall, light to moderate drinking does not appear to impair cognition in younger subjects and actually seems to reduce the risk of dementia and cognitive decline in older subjects.

The underlying role of aggressivity in the relation between executive functioning and alcohol consumption

The research literature on the relation between cognitive functioning and alcohol consumption is inconsistent and difficult to interpret. The purpose of this study was to test a causal model that might help reconcile some of these conflicts. The model specifies that aggressivity is an important intermediary mechanism underlying the relation between executive functioning (EF) and alcohol consumption. Participants were 310 (152 men and 158 women) healthy social drinkers between 21 and 35 years of age tested in a laboratory setting. EF was measured with a battery of neuropsychological tests. Aggressivity and alcohol consumption (as well as cigarette and drug use frequency) were measured with self-report and interview formats. Aggressivity played a mechanistic role in the relation between EF and alcohol/drug use for men but not for women. Women evinced some unexpected positive relations between EF and alcohol use. This study serves as a first step in trying to reconcile previous inconsistent findings regarding the relation between cognitive functioning and alcohol use by demonstrating that a better understanding of this relation involves considering aggressivity as an intermediary variable.

Alcohol alters rat adrenomedullary function and stress response

Most alcohol researchers do not address the effects of intoxication on the sympatho-adrenomedullary system response to stressful situations. We previously determined that rats consuming nearly 9 g ethanol (EtOH) per kg body weight per day in liquid diet form for 1 week increased adrenal gene expression of enzymes for catecholamine synthesis that was further elevated by acute IMMO. We hypothesized that the response to chronic mild stressors would also be altered after consumption of lower concentrations of EtOH in drinking water. Two experiments were conducted: 10% w/v for 4 weeks or 6% w/v for 7 weeks +/- wire mesh restraint (WMR). These were compared with ad libitum (adlib) and pair-fed control rats. Adrenal gene expression of catecholamine synthesizing enzymes was assayed. Tyrosine hydroxylase gene expression was elevated 80% to 90% by alcohol consumption in both experiments (P < 0.001) compared with adlib control rats. Dopamine betab-hydroxylase and phenylethanolamine-N-methyl transferase gene expressions were unaffected by 10% alcohol (P > 0.05) but were increased by 6% alcohol (P < 0.01). WMR decreased already elevated gene expression of all three enzymes. Pair feeding to 6% EtOH drinkers also increased gene expression for the three enzymes but was decreased by WMR, although not to levels of adlib rats. Increased gene expression for adrenal synthesis of catecholamines in response to repeated alcohol consumption increases the likelihood that the subject can respond physiologically to acute or chronic stress. This may have life-saving consequences in humans and in animals known to consume fermented materials and may contribute to increased aggressive behavior.

Effects of moderate alcohol consumption on the central nervous system

The concept of moderate consumption of ethanol (beverage alcohol) has evolved over time from considering this level of intake to be nonintoxicating and noninjurious, to encompassing levels defined as "statistically" normal in particular populations, and the public health-driven concepts that define moderate drinking as the level corresponding to the lowest overall rate of morbidity or mortality in a population. The various approaches to defining moderate consumption of ethanol provide for a range of intakes that can result in blood ethanol concentrations ranging from 5 to 6 mg/dl, to levels of over 90 mg/dl (i.e., approximately 20 mM). This review summarizes available information regarding the effects of moderate consumption of ethanol on the adult and the developing nervous systems. The metabolism of ethanol in the human is reviewed to allow for proper appreciation of the important variables that interact to influence the level of exposure of the brain to ethanol once ethanol is orally consumed. At the neurochemical level, the moderate consumption of ethanol selectively affects the function of GABA, glutamatergic, serotonergic, dopaminergic, cholinergic, and opioid neuronal systems. Ethanol can affect these systems directly, and/or the interactions between and among these systems become important in the expression of ethanol's actions. The behavioral consequences of ethanol's actions on brain neurochemistry, and the neurochemical effects themselves, are very much dose- and time-related, and the collage of ethanol's actions can change significantly even on the rising and falling phases of the blood ethanol curve. The behavioral effects of moderate ethanol intake can encompass events that the human or other animal can perceive as reinforcing through either positive (e.g., pleasurable, activating) or negative (e.g., anxiolysis, stress reduction) reinforcement mechanisms. Genetic factors and gender play an important role in the metabolism and behavioral actions of ethanol, and doses of ethanol producing pleasurable feelings, activation, and reduction of anxiety in some humans/animals can have aversive, sedative, or no effect in others. Research on the cognitive effects of acute and chronic moderate intake of ethanol is reviewed, and although a number of studies have noted a measurable diminution in neuropsychologic parameters in habitual consumers of moderate amounts of ethanol, others have not found such changes. Recent studies have also noted some positive effects of moderate ethanol consumption on cognitive performance in the aging human. The moderate consumption of ethanol by pregnant women can have significant consequences on the developing nervous system of the fetus. Consumption of ethanol during pregnancy at levels considered to be in the moderate range can generate fetal alcohol effects (behavioral, cognitive anomalies) in the offspring. A number of factors--including gestational period, the periodicity of the mother's drinking, genetic factors, etc.--play important roles in determining the effect of ethanol on the developing central nervous system. A series of recommendations for future research endeavors, at all levels, is included with this review as part of the assessment of the effects of moderate ethanol consumption on the central nervous system.

Cross-Cultural and Cognitive Factors Examined in Groups of Adolescent Drinkers

The purpose of this study was to examine the relationship between ethnicity, cognitive level, gender, drug use, and adolescent alcohol abuse. A sample of 194 white, black and Hispanic students from two high schools and one college participated in the study. The results indicated that whites report drinking more often; using alcohol more often to relieve tension; and experiencing more peer influence to drink than blacks or Hispanics. There was a significant correlation between cognitive development and degree of alcohol abuse for females, but not for males. There was no difference between high school seniors and college freshmen on drinking behavior or drinking due to stress, but there were differences between these students and high school freshmen. Peer pressure to drink was significantly greater for high school seniors than for college freshmen. While this study was exploratory, the findings offer plausible and potentially useful contributions to identifying and treating the adolescent drinker.

Effect of social drinking on neuropsychological performance

The effects of social drinking on neuropsychological function have been assessed in a group of healthy male volunteers. Subjects were divided into three groups according to their daily alcohol consumption: (1) 40 g or less (n = 93), (2) 41-80 g (n = 22), (3) 81-130 g (n = 16). Group 1 had been drinking at the present level for a mean of 12.6 years, group 2 for 16.9 years and group 3 for 15.1 years; the differences are not significant. There are no significant differences on any neuropsychological tests variables between groups 1 and 2. However, subjects in group 3 were found to perform at a significantly lower level than groups 1 and 2 on the Rey Auditory Verbal Learning Test, the Austin Maze, and the Little Man and Spatial Memory Tests of the Bexley Maudsley Automated Psychological Screening Test. The pattern of deficits found in heavy social drinkers is less severe but otherwise similar to that found in alcoholics.

High alcohol consumption, liver toxic drugs and brain damage--a population study

Computed tomography (CT) of the brain was performed in a random sample of 195 men to investigate the relationship between alcohol drinking and brain damage. This sample from the general population was divided into subsamples on the basis of their self-reported loss of control over drinking, morning drinks and blackouts. Three groups with different degrees of alcohol consumption were distinguished and the only differences in CT findings were a significantly higher frequency of frontal lobe atrophy with increasing alcohol consumption. The consumption of hepatotoxic drugs was also investigated and the following were the types of drug used: antiarrhythmics, antiepileptics, antibiotics, antiphlogistics, mixed analgetics, sulphonamides, benzodiazepines and derivatives of phenothiazines, all of which are metabolized by way of the liver. The material was divided into four groups with regard to both alcohol consumption and use of hepatotoxic drugs: Group IA, low or moderate alcohol consumption and no use of such drugs; IB, low or moderate alcohol consumption with use of such drugs; IIA, high alcohol consumption with no use of such drugs; and IIB, high alcohol consumption with use of such drugs. Group IIB was found to have a higher incidence of cortical and subcortical changes than group IA. The results indicate that drug use influences the incidence of cortical and subcortical aberrations. It is concluded that there is a typical frontal lobe atrophy associated with alcohol abuse; thus with increasing alcohol ingestion there is accelerated shrinkage of the brain, the frontal lobe being the first part affected. The groups with alcohol abuse who used hepatotoxic drugs show a picture of cortical changes and also of subcortical aberrations, expressed as an increased anterior horn index and widening of the third ventricle.

Neuropsychological performance of young nondrinkers, social drinkers, and long- and short-term sober alcoholics

Neuropsychological performance of 23-42-year-old males with diverse drinking histories was assessed. Comparisons were made among nondrinkers, social drinkers, short-term sober (less than 30 days) alcoholics and long-term sober (greater than 30 days) alcoholics. Results of these comparisons provided little support for the notion that neurotoxic effects of chronic alcohol consumption are directly related to cognitive impairment. Instead, these results suggested that performance differences among the groups were more closely related to subclinical withdrawal symptoms or native ability than to long-term alcohol consumption. Because none of the dependent measures was related to length of abstinence, and because Wechsler's Adult Intelligence Scale-R Vocabulary differences among groups paralleled neuropsychological test performance differences, it is suggested that differences among groups may reflect differences in native ability. In addition, there were no differences between social drinkers and nondrinkers, nor were there any significant correlations among drinking variables and performance of social drinkers, providing further evidence against a direct relationship between alcohol consumption and cognitive performance.

The hangover hypothesis and the influence of moderate social drinking on mental ability

The "hangover" hypothesis proposes that there is some residual effect of low to moderate alcohol intake on the nervous system after the blood alcohol level has returned to zero. This notion has been invoked to explain the putative effects of moderate alcohol consumption on mental ability. We evaluated the hangover hypothesis by attempting to predict cognitive performance from self-reports of alcohol consumed during the week prior to testing. We found no meaningful evidence to support the notion that moderate alcohol ingestion produces a measurable toxic effect on brain function after the period of acute intoxication.

Brain impairment in social drinkers? No cause for concern

Correlations between measures of alcohol consumption and cognitive test scores have been interpreted to reflect a chronic toxic effect of ethanol on brain function in light to moderate social drinkers. However, the data indicate that there is little support across research groups for any specific relationship and, at best, the effect of alcohol consumption accounts for only a small proportion of variance. Consideration of test validity suggests that the principal measure of ability used in this research is not capable of elucidating cerebral deficit. Further, the pattern of observed correlations is not consistent with the assumption that the putative effects of social drinking involve deficits less severe but similar in type to those seen in chronic alcoholics. Instead, an association between innate ability, demographic variables, and drinking behavior in the general population is the most parsimonious explanation of all the data.

The impact of fathers' drinking on cognitive loss among social drinkers

This chapter examines cognitive loss in social drinkers. The question of concern is whether the relationship between increased levels of alcohol consumption and reduced sober cognitive performance is misspecified. In particular, does reduced abstraction performance in social drinkers result from parental heavy drinking rather than, as we have proposed, from social drinkers' current use of alcohol. Because offspring of alcoholics may be at high risk for cognitive deficits even in childhood, these deficits may be transmitted in alcoholic families. Thus, the relationship between increased drinking and sober cognitive loss might be eliminated if parental drinking is controlled. We report here, however, that the effects of current alcohol use on abstraction performance in a representative sample of employed men and women cannot be accounted for by fathers' drinking. Our findings indicate the need for further research on both the cognitive effects of parental drinking and current alcohol use.

The continuity hypothesis: the relationship of long-term alcoholism to the Wernicke-Korsakoff syndrome

Although alcoholic Korsakoff's syndrome has traditionally been considered an acute disorder related to a nutritional deficiency, recent evidence demonstrating that ethanol may be neurotoxic has raised the possibility that the perceptual, problem-solving, and memory deficits associated with this chronic neurological disorder may develop slowly over decades of alcohol abuse. A review of the recent cognitive literature provides only limited support for this "continuity hypothesis." Long-term alcoholics, as with patients with alcoholic Korsakoff's syndrome, are impaired on numerous visuoconceptual and learning tasks, but there is little or no evidence that the information-processing deficits underlying the two patient groups' anterograde memory problems are similar. Furthermore, experimental and clinical studies of retrograde amnesia have noted only mild remote memory impairments in non-Korsakoff alcoholics as well as clear indications that alcoholic Korsakoff patients' severe loss or access to remote memories occurs acutely with the onset of Wernicke's encephalopathy. It is concluded that while the continuity hypothesis has heuristic value, there is still insufficient evidence to place the Korsakoff patient, the detoxified long-term alcoholic, and the heavy social drinker at different points on a single continuum of cognitive impairment.

Alcohol use and cognitive functioning in men and women college students

Two studies of the relationship between alcohol consumption and cognitive functioning in men and women college students are presented. Study 1 showed several predicted relationships of decreased cognitive performance on various tests with increased quantity of alcohol per occasion and total lifetime consumption in both women and men. Study 2a was designed to replicate study 1, but the pattern of relationship of cognitive and consumption variables was quite different, e.g., increased cognitive performance was associated with increased quantity per occasion for several tests in males. Study 2b was designed to demonstrate reversibility of the negative effects of consumption on cognition by randomly assigning half of the subjects to abstain for two weeks. Reversibility was not demonstrated. Difficulties in studying these effects in college students are discussed.

Cognitive deficits and morphological cerebral changes in a random sample of social drinkers

A random sample of 200 men and 200 women taken from the general population as well as subsamples of 31 male and 17 female excessive social drinkers were investigated with neuropsychological tests and computed tomography of the brain. Relatively high alcohol intake per drinking occasion did not give evidence of cognitive deficits or morphological cerebral changes. However, in males, mild cognitive deficits and morphological cerebral changes as a result of high recent alcohol intake, particularly during the 24-hr period prior to the investigation, were observed. When excluding acute effects of recent alcohol intake, mild cognitive deficits but not morphological cerebral changes that are apparently due to long-term excessive social drinking were observed in males. In females there was no association between the drinking variables and cognitive deficits or morphological cerebral changes, probably due to their less advanced drinking habits. It is suggested that future risk evaluations and estimations of safe alcohol intake should take into consideration the potential risk for brain damage due to excessive social drinking. However, it is premature to make any definite statements about safe alcohol intake and the risk for brain damage in social drinkers from the general population.