Alcohol acts as a depressant drug, meaning it slows down the activity of the central nervous system by reducing the speed of signals in the brain. The extent of these effects depends on the blood alcohol content (BAC), which measures the percentage of alcohol present in the bloodstream. BAC typically ranges from 0% to over 0.4%, with increasing levels causing progressively stronger effects on the body and brain.
At low BAC levels, up to about 0.06%, individuals often experience mild relaxation and lowered inhibitions, which can enhance social interactions. Despite the common belief that a nightcap aids sleep, alcohol actually disrupts REM sleep, the deepest and most restorative phase, leading to poorer sleep quality.
As BAC rises from approximately 0.07% to 0.2%, impairment becomes more pronounced. This range is associated with increased risk-taking behaviors, impaired motor coordination, and slurred speech. Notably, a BAC of 0.08% is the legal driving limit in most parts of the United States, reflecting the point at which cognitive and motor impairments significantly increase the danger of operating a vehicle. Alcohol-related impairments contribute to about 30% of traffic fatalities and a large proportion of accident-related hospitalizations.
At higher BAC levels, from 0.2% to 0.4%, severe impairment occurs, including greatly reduced motor control, speech difficulties, and a heightened risk of alcohol poisoning. Alcohol poisoning results from the depressant effect on the brain’s respiratory center, which controls breathing. This respiratory depression can begin around a BAC of 0.25% to 0.3%, posing a life-threatening risk. Medical intervention can often reverse these effects if administered promptly.
Beyond a BAC of 0.4% to 0.45%, the risk of death increases sharply due to critical suppression of vital central nervous system functions, potentially leading to respiratory failure and cessation of bodily functions.
Throughout all BAC levels, the likelihood and severity of hangovers increase. Alcohol is a diuretic, causing increased urination that leads to dehydration and loss of electrolytes. Combined with the buildup of toxic byproducts like acetaldehyde, this dehydration contributes to hangover symptoms such as headache, nausea, and fatigue. Despite many purported remedies, the only effective treatment for a hangover is time, along with rehydration to restore fluid and electrolyte balance.
It is important to avoid taking acetaminophen (a common painkiller) during or after drinking alcohol, as both substances are metabolized by the liver. Concurrent use can overwhelm the liver’s capacity, increasing the risk of liver damage, especially in individuals who consume alcohol regularly. While occasional use may not cause significant harm, caution is advised to prevent compounded liver stress.
