I attended a conference several years ago on conceptualization and treatment of dual diagnoses: individuals with a mental health issue as well as a substance abuse problem. The conference was top notch, presenting a wide range of information on the subject of excessive drug and alcohol use. One part of the presentation that caught my eye was the information discussed in this article, which discusses how individuals who have a low physiologic response to alcohol tend to have more significant problems with alcohol.
What is meant by low physiologic response is that, for most people, they will start to experience the effects of alcohol consumption after 1-2 drinks; from there on, they will continue to experience an increase in these effects (on speech, relaxation, etc.) with additional drinks. Low responders, on the other hand, experience only minimal "pre-intoxication" effects - they will look almost the same at six beers as they did after one beer. The problem is that after the seventh beer, both types of individuals look the same - the low responder simply makes up all of that physiologic ground with one more drink, catching up in a hurry. From the article:
"If a person needs more alcohol to get a certain effect, that person tends to drink more each time they imbibe," explained Marc A. Schuckit, director of the Alcohol Research Center, Veterans Affairs San Diego Healthcare System, professor of psychiatry at the University of California, San Diego, and corresponding author for the study.
"Other studies we have published have shown that these individuals also choose heavy drinking peers, which helps them believe that what they drink and what they expect to happen in a drinking evening are 'normal,'" he said. "This low LR, which is perhaps a low sensitivity to alcohol, is genetically influenced."
So why is this a problem? Well, in addition to the information above, it is important to note that experiencing some effect of alcohol use, without becoming intoxicated, serves as a warning for people that "they've had enough." The effect after two or three drinks, whether initially desired or not, is enough. Individuals with low response to alcohol, however, do not benefit from such warnings - they are able to drink and drink, right up to the point where they experience the effects rapidly, and have now consumed too much. Their body doesn't give them a "head's up" like most folks. This contrast is very easy to demonstrate on a graph, a bit harder to describe in words, but hopefully you get the gist. Also from the article:
"Because alcoholism is genetically influenced, and because a low LR is one of the factors that adds to the risk of developing alcoholism," said Schuckit, "if you're an alcoholic, you need to tell your kids they are at a four-fold increased risk for alcoholism. If your kid does drink, find out if they can 'drink others under the table,' and warn them that that is a major indication they have the risk themselves. Keep in mind, however, that the absence of a low LR doesn't guarantee they won't develop alcoholism, as there are other risk factors as well."
The flip side to this, of course, is that even if both parents of an individual are alcoholics, it isn't "written in stone" that the person themself will be. If I recall correctly, and individual with niether parent as an alcoholic has a 12% chance (roughly) of developing alcoholism; one parent=25% chance, and two parents roughly a 46% chance. These statistics can be helpful in overcoming doom-n-gloom in a person's consideration of their future regarding alcohol, that they aren't automatically destined for severe alcohol problems, especially if they are willing to put in the effort necessary to address areas of concern.