alcoholism

Alcohol and marijuana use in adolescence linked to impaired white-matter integrity

A brain-imaging study shows adolescents who abuse alcohol and marijuana show poorer white-matter integrity, with alcohol associated with continuing damage to wiring in prefrontal regions.

Chronic use of alcohol and marijuana during youth has been associated with poorer neural and cognitive function, which appears to continue into adulthood. A new study looking specifically at white-matter changes provides more support for the idea that adolescent brains may be at particular risk from the damage that substance abuse can bring.

The brain-imaging study compared 41 adolescents (aged 16-20) with extensive marijuana- and alcohol-use histories by mid-adolescence with 51 adolescents with no such history. The study found that substance users showed poorer white matter integrity in seven tracts (right and left superior longitudinal fasciculus, right posterior thalamic radiations, right prefrontal thalamic fibers, right superior temporal gyrus white matter, right inferior longitudinal fasciculus, left posterior corona radiata).

Two brain scans were taken, at baseline and at 18 months. Substance use interviews were given every six months.

More alcohol use during the interval was associated with worse integrity in both the right and left superior longitudinal fasciculi, above and beyond baseline values in these bundles. Marijuana use didn’t predict change over time. Those who had a history of more risk-taking behaviors showed poorer integrity of the right prefrontal thalamic fibers.

The findings add to previous research showing white matter problems in youth with substance-use histories. The study points to alcohol use during adolescence being particularly problematic. It also suggests that youth who engage in risk-taking behaviors may tend to have poorly developed fronto-thalamic tracts.

All of this is particularly worrying because it is thought that maturation of the brain during adolescence is the foundation for self-control, suggesting that substance abuse during this period may have long-lasting effects on the individual’s ability to plan, organize, and self-regulate.

Reference: 

[3210] Bava, S., Jacobus J., Thayer R. E., & Tapert S. F.
(2012).  Longitudinal Changes in White Matter Integrity Among Adolescent Substance Users.
Alcoholism: Clinical and Experimental Research. n/a - n/a.

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The wrong genes mean even moderate drinking in pregnancy can affect a child's IQ

December, 2012

A large study suggests that even a few drinks a week can negatively affect the developing fetus, but only if the woman has specific gene variants.

It’s always difficult in human studies to disentangle the effects of lifestyle factors. Alcohol is a case in point, and in particular the vexed question of whether any alcohol is safe during pregnancy. A new study, however, has avoided the complication of co-occurring lifestyle and environment factors by looking directly at genetic variants.

This study, believed to be the first substantial one of its kind, used genetic variation to investigate the effects of moderate (<6 units of alcohol per week) drinking during pregnancy among a large group of women and their children. Since the individual variations that people have in their DNA are not connected to lifestyle and social factors, the approach removes that potential complication.

The study, involving 4,167 children, found that four genetic variants in alcohol-metabolizing genes were strongly related to lower IQ at age eight. But this effect was only seen among the children of women who were moderate drinkers (heavy drinkers were not included in the study), pointing to the effect requiring exposure to alcohol in the womb.

Ten SNPs from four genes previously implicated in alcohol metabolism, intake, or dependency, were analyzed. Four SNPs (particular variants) were related to children’s scores on the cognitive test (WISC), of which three are rare and one quite common. There was an additive effect, with carriers of multiple ‘bad’ alleles being more affected.

There was some evidence that only drinking one or two drinks a week was not harmful to the fetus, but because the numbers of women were relatively small, and individual variability was high, this can’t be assessed with any great certainty.

The critical factor appears to be metabolism of alcohol, with mothers who are ‘fast' metabolizers being safer for their fetus than mothers who metabolize alcohol more slowly.

Mothers' alcohol intake was based on questionnaires completed when they were 18 weeks and 32 weeks pregnant. ‘Moderate’ was defined as between one and six drinks a week. All participants were of white-European origin.

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Adolescent binge drinking can damage spatial working memory

August, 2011

This study finds that adolescent females are particularly vulnerable to the effects of binge drinking, and points to specific changes in brain activation patterns seen in binge drinkers.

Binge drinking occurs most frequently among young people, and there has been concern that consequences will be especially severe if the brain is still developing, as it is in adolescence. Because of the fact that it is only some parts of the brain — most crucially the prefrontal cortex and the hippocampus — that are still developing, it makes sense that only some functions will be affected.

I recently reported on a finding that binge drinking university students, performed more poorly on tests of verbal memory, but not on a test of visual memory. A new study looks at another function: spatial working memory. This task involves the hippocampus, and animal research has indicated that this region may be especially vulnerable to binge drinking. Spatial working memory is involved in such activities as driving, figural reasoning, sports, and navigation.

The study involved 95 adolescents (aged 16-19) from San Diego-area public schools: 40 binge drinking (27 males, 13 females) and 55 control (31 males, 24 females). Brain scans while performing a spatial working memory task revealed that there were significant gender differences in brain activation patterns for those who engaged in binge drinking. Specifically, in eight regions spanning the frontal cortex, anterior cingulate, temporal cortex, and cerebellum, female binge drinkers showed less activation than female controls, while male bingers exhibited greater activation than male controls. For female binge drinkers, less activation was associated with poorer sustained attention and working memory performances, while for male binge drinkers, greater activation was linked to better spatial performance.

The differences between male binge drinkers and controls were smaller than that seen in the female groups, suggesting that female teens may be particularly vulnerable. This is not the first study to find a gender difference in the brains’ response to excess alcohol. In this case it may have to do, at least partly, with differences in maturity — female brains mature earlier than males’.

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Young binge drinkers less able to learn new verbal information

July, 2011

Binge drinking university students, regardless of gender, performed more poorly on tests of verbal memory, but not on a test of visual memory.

Following animal research indicating that binge drinking damages the hippocampus, and other research showing that this learning and memory center is still developing during adolescence, a new study has investigated the effects of binge drinking on learning in university students. The study, involving 122 Spanish university students (aged 18-20), of whom half engaged in binge drinking, found a clear association between binge drinking and a lower ability to learn new verbal information.

Specifically, binge drinkers were more affected by interference in the Rey Auditory Verbal Learning Test, and remembered fewer words; they also performed worse on the Weschler Memory Scale-3rd ed. (WMS-III) Logical Memory subtest, both on immediate and delayed recall. However, there were no differences between the two groups on the WMS-III Family Pictures subtest (measuring visual declarative memory).

These results persisted even after controlling for other possible confounding variables such as intellectual levels, history of neurological or psychopathological disorders, other drug use, or family history of alcoholism.

The genders were evenly represented in both groups. Interestingly, and in contradiction of some other research, women were not found to be more vulnerable to the neurotoxic effects of binge drinking.

Reference: 

[2298] Parada, M., Corral M., Caamaño‐Isorna F., Mota N., Crego A., Holguín S R., et al.
(Submitted).  Binge Drinking and Declarative Memory in University Students.
Alcoholism: Clinical and Experimental Research.

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Surgical skills affected by previous-day excess alcohol consumption

May, 2011

Simulated laparoscopic surgery was impaired in both novices and experts on the day following an evening during which excessive alcohol was consumed.

Laparoscopic surgery makes intense demands on cognitive, perceptual and visuospatial abilities, rendering it particularly vulnerable to the effects of alcohol (and also making it a sensitive indicator). In a real-world type experiment, students and experts participated in a study looking at the effects of previous-night’s carousing on next-day’s performance on the Minimally Invasive Surgical Trainer Virtual Reality (for which all participants received training, providing baseline scores).

The first experiment involved 16 male final-year science students, of whom 8 were asked to consume alcohol freely at a group dinner, while the other 8 went to a dinner at which no alcohol was served. The second experiment involved eight laparoscopic experts, all of whom were asked to consume alcohol freely at their group dinner. Participants were tested on the simulator the next day at 9:00 a.m., 1:00 p.m. and 4:00 p.m.

Among the students, those who had consumed excessive alcohol performed considerably worse in terms of time, errors and economy of diathermy (ability to perform technique designed to produce local application of heat), and showed considerable performance variability. Their performance in terms of errors and diathermy was significantly impaired compared to that of the control group. Differences in the time it took participants to perform the tasks were only significant at 9:00 a.m.

Experts were (thankfully!) less impaired by their night out. Nevertheless, they made more errors than they had at baseline, and the difference at 1:00 p.m. was statistically significant. They were also significantly slower during the 1:00 p.m. tests. Performance had returned to baseline levels by 4:00 p.m.

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Adolescent brain vulnerable to binge drinking and tobacco

April, 2011

Binge drinking occurs most often in adolescents, and most smokers also begin at this time. Two new studies suggest that the impact of these activities on their still-developing brains is likely to be long-lasting.

Binge drinking is, unfortunately, most common among adolescents (12-20 years). But this is a time when brains are still developing. Does this make them more vulnerable to the detrimental effects of excessive alcohol?

A study involving adolescent mice has revealed that not only did an alcoholic binge reduce the activity of many neurotransmitter genes, but that gene expression in adulthood was even more seriously reduced. Although this deficit didn’t translate into problems with spatial learning, adult mice that had been exposed to excess alcohol in adolescence were significantly worse on a reversal learning task. Moreover, certain brain regions (the olfactory bulb and basal forebrain) were smaller.

In humans, it is thought that these impairments might translate into greater difficulty in adapting to changed situations, in evaluating consequences and controlling impulses.

Similarly, another recent study involving teenagers (15-21) has found that activity in the prefrontal cortex varied according to how heavily they smoked, with those who smoked most heavily having the least activity.

The 25 smokers and 25 non-smokers were tested on a Stop-Signal Task, which tests a person’s ability to inhibit an action. Despite the differences in activity level, smokers and non-smokers performed similarly on the task, suggesting that other brain areas are in some way compensating for the impaired prefrontal cortex. Nevertheless, reduced activity in the prefrontal cortex, which is still developing in adolescence, does suggest long-term consequences for decision-making and cognitive control.

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Cognitive effects of heavy alcohol and marijuana use in adolescents

November, 2010

Alcohol and marijuana abuse associated with specific cognitive impairments in adolescents, but more surprisingly family history of substance abuse can also have an effect.

A study involving 48 adolescents, of whom 19 had been diagnosed with substance abuse/dependence, and 14 had a family history of substance abuse but no history of personal use, has found that greater alcohol use was associated with a significant decrease in attention and executive function (which is involved in planning and decision-making), while greater marijuana use was associated with poorer memory. Adolescents in the substance abuse group had lower scores in attention, memory, and processing speed, compared to the other groups, while those with a family history of abuse (but no personal history) had poorer visuospatial ability.

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Fetal alcohol exposure associated with a decrease in cognitive performance

November, 2010

Fetal exposure to large amounts of alcohol is found to be associated with reduced cognitive efficiency in perception, attention and recognition memory, in older children.

Data from 217 children from Inuit communities in Arctic Quebec (average age 11), of whom some had mothers that reported binge drinking during pregnancy, has revealed that the alcohol-exposed group, while similar to the control in accuracy and reaction time, showed a significant differences in their brains’ electrical activity while doing those tasks (a Go/No-go response inhibition task and a continuous recognition memory task). The differences suggest that fetal alcohol exposure is associated with reduced efficiency in the initial extracting of the meaning of a stimulus, reduced allocation of attention to the task, and poorer conscious recognition memory processing.

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Alcohol dependence damages both episodic memory and awareness of memory

September, 2010

Adding to the evidence that chronic alcohol abuse produces various cognitive deficits, a new study reveals that it’s also linked to poor metamemory.

Metamemory (understanding your own memory capabilities) is important for learning. Now a study involving 28 alcoholics has found that, compared to controls, they not only performed more poorly on a test of episodic memory, but they were less accurate in their assessments of how good their memory was. The episodic memory task involved learning 20 pairs of items, followed by a recall and a recognition test 20 minutes later. Before the recognition test, participants rated their ability to recognize each nonrecalled word among 4 items. The alcoholics were relatively unaware of their memory deficits and believed that their memory was much better than it was. On a questionnaire of their general memory capacities, they also tended to report themselves as much more capable than they were. Their over-estimation was related to their low performance on tests of executive function.

The finding has implications for any recovery program, since alcoholics will tend to believe that they have mastered any learning long before they have.

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Prenatal meth exposure associated with brain abnormalities

March, 2010

An imaging study has revealed that children (aged 5-15) whose mothers abused methamphetamine and alcohol during pregnancy had structural abnormalities in the brain that were more severe than those seen in children whose mothers abused alcohol alone.

An imaging study has revealed that children (aged 5-15) whose mothers abused methamphetamine and alcohol during pregnancy had structural abnormalities in the brain that were more severe than those seen in children whose mothers abused alcohol alone. In particular, the striatal region was significantly smaller, and within the group, size of the caudate correlated negatively with IQ. Limbic structures, in particularly the cingulate cortex and the right inferior frontal gyrus, were significantly bigger. The striatal and limbic structures are also known to be particularly affected in adult methamphetamine abusers.

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