Public Release:  Alcohol impairs executive cognitive functioning much longer than expected

Alcoholism: Clinical & Experimental Research

  • Executive cognitive functioning (ECF) includes cognitive abilities such as abstract reasoning, planning, and the capacity to govern self-directed behavior.
  • Researchers have found that ECF is more impaired during the descending limb of the blood alcohol concentration curve, when people no longer feel stimulated by alcohol.
  • These findings indicate that intoxication effects last much longer than previously believed.

Executive cognitive functioning (ECF) encompasses a number of 'higher order' cognitive abilities, such as attention, abstract reasoning, organization, mental flexibility, planning, self-monitoring, and the ability to use external feedback to moderate personal behavior. A study in the May issue of Alcoholism: Clinical & Experimental Research has confirmed that not only does alcohol impair ECF but, surprisingly, this effect is more pronounced on the descending rather than the ascending trajectory (or limb) of the blood alcohol concentration (BAC) curve.

"Executive functioning is basically a metaphor for frontal lobe functioning," explained Robert O. Pihl, professor of psychology and psychiatry at McGill University and first author of the study. "This area of the brain, the prefrontal cortex, arguably defines us as a species; it is roughly 120 percent larger in humans than in our closest primate relatives. In fact, some Russian neurophysiologists refer to it as the area of the brain that pulls the past, the present, and the future together. In other words, it puts things in context."

"Research on alcohol's effects on ECF is important primarily because it sheds light on the relationship between intoxication and aggression," added Jordan B. Peterson, associate professor of psychology at the University of Toronto. "Approximately 50 percent of murderers are intoxicated at the time of their crime. The same holds true of their victims."

Study participants (n=41) were divided into two groups: 21 subjects were given 1.32 ml of 95 percent alcohol per kg of body weight mixed with orange juice; the remaining 20 were given a placebo. Participants were randomly assigned to either an ascending or descending limb group. (When people drink alcohol, stimulation is initially prominent, while blood alcohol levels are rising during the 'ascending limb' of the BAC curve. During the 'descending limb' of the BAC curve, when blood alcohol levels are falling, sedation becomes the prominent experience.) All of the participants were given six tests of ECF when a breath measure of their BAC reached 0.08.

Intoxicated participants on both limbs demonstrated ECF impairment. However, the descending alcohol limb group showed greater ECF impairment than their ascending limb counterparts, particularly in spatial functioning.

"Our results were unexpected," said Pihl. "Based on prior research, we had expected cognitive deficiencies to be greater on the ascending limb. Although 'intoxication' clearly lasts a long time, you don't have the same feedback of feeling intoxicated on the descending limb. You have a different perception of what your decrements are when you 'feel' intoxicated and energized versus when you think, 'hey, I'm getting sober.' Yet our findings show that even when you're at the same blood alcohol level on the downward limb, you have more pronounced deficits."

This finding has important ramifications for behaviors such as driving, Pihl added. "People who think they've waited their two hours before driving home may need to actually wait six hours. Or else, maybe at the time when you least expect it, you're the most vulnerable."

"The subjective effects that alcohol drinkers pursue are most likely experienced during the short, ascending limb," said Peterson. "Conversely, the descending limb lasts a very long time. This means that the drinker in the process of re-attaining sobriety is likely to be more dangerous, for example, than the drinker who is still imbibing. As the authors point out, this may also be relevant with regards to impaired driving: it could be that the drinker at a BAC of 0.08 is less qualified to drive while immediately recovering from a drinking episode than while actively drinking."

Peterson praised Pihl's lab for its investigation of relatively high-dose alcohol administration, research that has become increasingly difficult in recent years. "However, such high doses appear absolutely necessary to produce the kind of cognitive effects reported in this manuscript," he said. "Furthermore, they are clearly in keeping with the levels of intoxication that drinkers reach when drinking for pleasure in bars and at parties". He suggested that future research examine how long the detrimental descending-limb cognitive effects last. "Are drinkers back to baseline cognitive function once their BACs fall to 0.04, for example, or are they still substantively impaired? Have they returned to baseline the next day, after sleeping through the sobering-up process, even if they still feel some hangover effects?" he asked.

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Alcoholism: Clinical & Experimental Research (ACER) is the official journal of the Research Society on Alcoholism and the International Society for Biomedical Research on Alcoholism. Co-authors of the ACER paper included: Sheila S. Paylan, Alyson Gentes-Hawn, and Peter N.S. Hoaken of the Department of Psychology and Psychiatry at Mcgill University in Montreal. The study was funded by the Canadian Institute of Health Research.

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