The types of behavior that begin occurring soon after people start drinking alcohol are collectively referred to as intoxication. This state includes impaired physical coordination and mental performance as well as changes in a person’s emotions, including a feeling of relaxation and a lessening of fear or anxiety over personal problems. Although for most people these initial sensations are usually pleasant, the effects of alcohol intensify as drinkers consume more alcohol. This leads to difficulty in how a person reacts and responds physically, mentally, and emotionally to what is happening around him or her.

The way alcohol affects people is complex, however, and the effects it creates change as people drink more and more. Although alcohol is a depressant, it acts more like a stimulant when people first take a drink. Moderate doses of alcohol increase blood flow, accelerate the heart rate, and stimulate brain cells to speed the transmission of nerve impulses. In Beyond the Influence: Understanding and Defeating Alcoholism, Katherine Ketcham and William F. Asbury explain that these physiological changes in turn create a feeling of emotional well-being, which is the main reason that people enjoy drinking:

We turn to alcohol for relaxation and stress reduction, and the drug delivers almost immediately by making us feel happy, energetic, and at peace with ourselves. These pleasurable, tension-relieving sensations are due to alcohol’s stimulating effects on the body, particularly the brain and the heart.

In an average person, one standard drink will produce a light feeling of pleasantness or exhilaration. People who consume two glasses of wine or bottles of beer will tend to have a heightened feeling of relaxation coupled with a decrease in fine motor skills, and those who have three drinks will begin to have slower physical reaction times, decreased muscular control, and slurred speech. Even at this stage, many people will still be able to function almost normally physically and mentally, although some drinkers, especially those who do not drink often, may begin to experience some problems.

However, the more people drink the more intoxicated they will become. And as the level of alcohol in their system rises, alcohol will begin creating new and quite different physical and mental reactions.

Blood Alcohol Level and Intoxication

The amount of alcohol in a person’s bloodstream is referred to as blood alcohol level (BAL) or blood alcohol concentration (BAC). It is recorded in milligrams of alcohol per 100 milliliters of blood; a blood alcohol concentration of 0.10 means that 1/10 of 1 percent of total blood content is alcohol. A reading of 0.10 percent is considered legal proof that a person is drunk in most states. The following are some examples of the observable effects of certain blood alcohol levels on occasional social drinkers (because of their higher tolerance, an alcoholic or problem drinker must have blood alcohol levels several times higher before alcohol will create the same effects in them).

At 0.03 to 0.05 percent, a flushed face, feeling of euphoria, and increased social confidence; at 0.50 to 0.15 percent, disturbed thinking and coordination, reduced self-control, irresponsible talk and behavior; at 0.15 to 0.25 percent, confused thinking, unsteady gait, slurred speech; at 0.25 to 0.40 percent, extreme confusion and disorientation, difficulty remaining upright, drowsiness, risk of falling into a coma (a state of deep unconsciousness from which the person cannot be aroused); 0.40 to 0.50 percent, risk of death due to cessation of breathing (although habitual drinkers may survive even such high levels).