During chronic alcohol consumption, the drinker often develops a tolerance to alcohol’s adverse effects. This means that the consumption of a constant amount of alcohol produces a lesser effect or increasing amounts of alcohol are needed to produce the same effect. That being said, tolerance may encourage increased and/or frequent alcohol consumption that may develop into a dependance as well as multiple organ damage.
There are several types of studied tolerances that are inspired by different scenarios.
Functional Tolerance
Alcohol heavily impacts GABA transmission, increasing its depressive effects on the nervous system. With chronic drinking, the GABA receptor system becomes less responsive to the effects of alcohol causing less relaxation, sleepiness and analgesia. Heavy drinkers display functional tolerance, even at a high BAC they show few signs of intoxication while in others the alcohol levels would be disabling or even fatal.
Acute Tolerance
- Can occur in a single drinking session.
- Individual is more impaired soon after drinking than later in consumption.
- Acute tolerance can prompt the drinker to consume more alcohol.
Environment-dependent Tolerance
- Often observed in social drinkers.
- Effects of chronic drinking are retarded if alcohol consumption occurs in the same environment or is accompanied by the same prompts.
- Study conducted observed subject’s heart rate in different drinking environments. Subjects who received alcohol in the same room had their heart rate increase to a lesser degree than those who drank in a new environment.
- Effect is commonly seen in bars, alcohol induces lesser effects in social outings because the environment is likely associated with drinking.
Learned Tolerance
- Tolerance can be increased by practicing a task while under the influence of alcohol.
- Tasks that require hand-eye coordination have been linked to learned tolerance.
Metabolic Tolerance
Metabolic tolerance occurs from the accelerated elimination of alcohol from the body due to an elevated metabolic response. In chronic drinkers, the liver produces more enzymes that break down alcohol to account for increased intake. That being said, the liver breaks down alcohol more efficiently thus, chronic drinkers need to consume more alcohol in order to achieve the desired effects. However, liver enzymes are also responsible for metabolizing other drugs so, an increase in enzyme activity may lead to adverse effects from an increase in reactive metabolites.