Key components to alcohol dependence, reports the Mayo Clinic, is the inability to quit drinking, symptoms of withdrawal occurring during periods of abstinence and needing more alcohol to achieve the same level of intoxication. For those who abuse alcohol, while you might not be physically addicted, the more you drink, the more you increase your tolerance.
What is Tolerance
Tolerance occurs when the body becomes accustomed to the drug, in this case alcohol. In an interview for ABC News, Christopher J. Welsh, M.D., addiction specialist, explained that after chronic drinking, the body needs more alcohol to get the same effect. Tolerance is one aspect of alcohol dependence.
Functional Tolerance
The National Institute on Alcohol Abuse and Alcoholism, NIAAA, defines functional tolerance as the reaction of the brain to disruption caused by alcohol abuse. For a chronic drinker, tolerance is characterized when he shows few obvious signs of intoxication, regardless of his blood-alcohol concentration, or BAC. For those who do not abuse alcohol, the same level of intoxication would cause obvious changes like difficulty walking, slurred speech, or incapacitation. The lack of physical impairment for an alcohol abuser would cause her to crave more alcohol.
Acute Tolerance
The National Institutes of Health indicates that acute tolerance occurs when a person shows few visible cues of inebriation during a single drinking session. A 1986 study published in the "Annals of Emergency Medicine" by lead researcher Boris Tabakoff, Ph.D., which was later used in the NIAAA report titled "Alcohol and Tolerance," researchers found that in some alcohol abusers, a person's impairment is more affected soon after beginning drinking compared to their impairment later in the same drinking session, even if their BAC is remains constant.
Learned Tolerance
When a task is learned while a person is under the influence of alcohol, it is known as behavioral augmentation. It leads to what the NIAAA calls "learned tolerance." In both animal and human studies, those who practiced a task while drinking performed better then those who learned the task while sober and attempted to perform it while drinking. Further, the knowledge that a person will receive a reward, such as money, for performing a task while under the influence developed a tolerance faster than those who were not offered a reward.
Biological Tolerance
Chronic alcohol abusers feel the effects of alcohol for shorter periods compared to social drinkers, according to the NIAAA, thanks to a metabolic process in which certain liver enzymes associated with metabolism is activated. This process is not only limited to the degradation of alcohol, however. At this stage, some alcohol abusers metabolize other drugs more quickly as well. For example, an increased breakdown of acetaminophen in the body can be toxic to the liver, which contributes to liver disease.
