The short-term effects of alcohol on the human body can take several forms.
Alcohol, specifically ethanol, is a potent central nervous system depressant, with a range of side effects. The amount and circumstances of consumption play a large part in determining the extent of intoxication; for example, consuming alcohol after a heavy meal causes alcohol to absorb more slowly. Hydration also plays a role, especially in determining the extent of hangovers. The concentration of alcohol in blood is usually measured in terms of the blood alcohol content.
Initially, alcohol generally produces feelings of relaxation and cheerfulness, but further consumption can lead to blurred vision and coordination problems. Cell membranes are highly permeable to alcohol, so once alcohol is in the bloodstream it can diffuse into nearly every biological tissue of the body. After excessive drinking, unconsciousness can occur and extreme levels of consumption can lead to alcohol poisoning and death (a concentration in the blood stream of 0.40% will kill half of those affected). Death can also occur through asphyxiation by vomit. An appropriate first aid response to an unconscious, drunken person is to place them in the recovery position.
Signs and symptoms
Alcohol is a highly-abused substance that greatly exacerbates sleep problems. During abstinence, residual disruptions in sleep maintenance and sleep architecture are the greatest predictors of relapse.
Moderate alcohol consumption and sleep disruptions
Moderate alcohol consumption 30-60 minutes before bedtime catalyzes disruptions in sleep maintenance and sleep architecture that are mediated by blood alcohol levels . Disruptions in sleep maintenance are most marked once alcohol has been completely metabolized from the body. Under conditions of moderate alcohol consumption where blood alcohol levels average 0.06-0.08 percent and decrease 0.01-0.02 percent per hour, an alcohol clearance rate of 4-5 hours would coincide with disruptions in sleep maintenance in the second half of an 8 hr sleep episode . In terms of sleep architecture, moderate doses of alcohol facilitate "rebounds" in rapid eye movement (REM) and stage 1 sleep; following suppression in REM and stage 1 sleep in the first half of an 8 hr sleep episode, REM and stage 1 sleep increase well beyond baseline in the second half. Moderate doses of alcohol also increase slow wave sleep (SWS) in the first half of an 8 hr sleep episode . Enhancements in REM sleep and SWS following moderate alcohol consumption are mediated by reductions in glutamatergic activity by adenosine in the central nervous system . In addition, tolerance to changes in sleep maintenance and sleep architecture develops within 3 days of alcohol consumption before bedtime .
Alcohol consumption and sleep improvements
Low doses of alcohol (one 12 oz. beer) are sleep-promoting by increasing total sleep time and reducing awakenings during the night. The sleep-promoting benefits of alcohol dissipate at moderate and higher doses of alcohol (two 12 oz beers and three 12 oz. beers, respectively) . Previous experience with alcohol also determines whether or not alcohol is a "sleep promoter" or "sleep disrupter." Under free-choice conditions, in which subjects chose between drinking alcohol or water, inexperienced drinkers were sedated while experienced drinkers were stimulated following alcohol consumption . In insomniacs, moderate doses of alcohol improve sleep maintenance .
Alcohol consumption and fatigue
Sleepiness influences the severity of alcohol consumption. Conditions of sleep deprivation encourage more episodes of alcohol consumption . Increased alcohol consumption during the winter months for Northern climate residents is attributed to escalations in fatigue .
Alcohol abstinence and sleep disruptions
Sleep and hormonal disruptions following withdrawal from chronic alcohol consumption are the greatest predictors of relapse . During abstinence, recovering alcoholics have attenuated melatonin secretion in the beginning of a sleep episode, resulting in prolonged sleep latencies . Escalations in cortisol and core body temperatures during the sleep period contribute to poor sleep maintenance .
Effect by dosage
Different concentrations of alcohol in the human body have different effects on the subject.
The following lists the effects of alcohol on the body, depending on the blood alcohol concentration or BAC. Remember that tolerance varies considerably between individuals.
Please note: the BAC percentages provided below are just estimates and used for illustrative purposes only. They are not meant to be an exhaustive reference; please refer to a healthcare professional if more information is needed.
Euphoria (BAC = 0.03 to 0.12%).
- Subject may experience an overall improvement in mood and possible euphoria.
- They may become more self-confident or daring; they may become more friendly or talkative, and/or social.
- Their attention span shortens. They may look flushed.
- Their judgment is not as good—they may express the first thought that comes to mind, rather than an appropriate comment for the given situation. See: in vino veritas
- They may have trouble with fine movements, such as writing or signing their name.
Lethargy (BAC = 0.09 to 0.25%)
- Subject may become sleepy.
- They have trouble understanding or remembering things, even recent events. They do not react to situations as quickly.
- Their body movements are uncoordinated; they begin to lose their balance easily, stumbling; walking is not stable.
- Their vision becomes blurry. They may have trouble sensing things (hearing, tasting, feeling, etc.).
Confusion (BAC = 0.18 to 0.30%)
- Profound confusion—uncertain where they are or what they are doing. Dizziness and staggering occur.
- Heightened emotional state—aggressive, withdrawn, or overly affectionate. Vision, speech, and awareness are impaired.
- Poor coordination and pain response. Nausea and vomiting sometimes occurs.
Stupor (BAC = 0.25 to 0.40%)
- Movement severely impaired; lapses in and out of consciousness.
- Subjects can slip into a coma; will become completely unaware of surroundings, time passage, and actions.
- Risk of death is very high due to alcohol poisoning and/or pulmonary aspiration of vomit while unconscious.
- Loss of bodily functions can begin, including bladder control, breathing, heart rate.
Coma (BAC = 0.35 to 0.50%)
- Unconsciousness sets in.
- Reflexes are depressed (i.e., pupils do not respond appropriately to changes in light).
- Breathing is slower and more shallow. Heart rate drops. Death usually occurs at levels in this range.
Ethanol inhibits the ability of glutamate to open the cation channel associated with the N-methyl-D-aspartate (NMDA) subtype of glutamate receptors. Alcohol sensitizes the N-methyl-D-aspartate (NMDAi) system of the brain, making it more receptive to the neurotransmitter glutamate. Stimulated areas include the cortex, hippocampus and nucleus accumbens, which are responsible for thinking and pleasure seeking. Another one of alcohol's agreeable effects is body relaxation, possibly caused by neurons transmitting electrical signals in an alpha waves-pattern; Alpha waves are observed (with the aid of EEGs) when the body is relaxed.
Alcohol has also been linked with lowered inhibitions, though it is unclear to what degree this is chemical versus psychological as studies with placebos can often duplicate the social effects of alcohol at low to moderate doses. Some studies have suggested that intoxicated people have much greater control over their behavior than is generally recognized, though they have a reduced ability to evaluate the consequences of their behavior. Behavioral changes associated with drunkenness are, to some degree, contextual. A scientific study found that people drinking in a social setting significantly and dramatically altered their behavior immediately after the first sip of alcohol, well before the chemical itself could have filtered through to the nervous system.
Areas of the brain responsible for planning and motor learning are dulled. A related effect, caused by even low levels of alcohol, is the tendency for people to become more animated in speech and movement. This is due to increased metabolism in areas of the brain associated with movement, such as the nigrostriatal pathway. This causes reward systems in the brain to become more active, and combined with reduced understanding of the consequences of their behavior, can induce people to behave in an uncharacteristically loud and cheerful manner.
Alcohol has been known to mitigate the production of ADH (antidiuretic hormone), which is a hormone that acts on the kidney, favoring water reabsorption in the kidneys during filtration. This occurs because alcohol confuses osmoreceptors in the hypothalamus, which relay osmotic pressure information to the posterior pituitary, the site of ADH release. Alcohol makes the osmoreceptors signal as if there was a too low osmotic pressure in the blood, which triggers an inhibition of ADH. Consequently, one's kidneys are no longer able to reabsorb as much water as they should be absorbing, leading to creation of excessive volumes of urine and subsequently overall dehydration.
Excessive dose
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