Monday, December 9, 2024

Intelligence and its association with alcohol problems

Many people are not subjected to Intelligence Quotient (IQ) tests when they are at high school; but students of my generation (the 1970s) in Australia were. This mattered a lot to me at the time, so I know what a stress it can be. It is therefore of interest as to whether one’s ability, as assessed at that time, does matter in later life — after all, the tests are done because IQ is claimed to be a strong predictor of various life outcomes, such as education, income and health.

High school success, as determined by exam results for instance, can matter a lot to your early life; for example if you want to get in to university (as I did). However, IQ is a somewhat different thing. Having a high IQ does not necessarily mean that you will do well at exams, as exams require a particular technique in order to succeed, and this technique can be learned, irrespective of whether you have a high IQ.

Now, clearly, “intelligence” has a rather abstract nature; and therefore IQ is a somewhat nebulous concept. [It is discussed further below.] Nevertheless, we can proceed with it in this post — recently, a study was published about the relationship between IQ as assessed when young and alcohol consumption much later in life; and I will discuss this here.


The study at hand is from the journal Alcohol and Alcoholism):

The report notes:
[Study group]: Study data were from 6,300 men and women who participated in the Wisconsin Longitudinal Study (WLS) of high-school students graduating in 1957. IQ scores were collected during the participants’ senior year of high school. In 2004, participants reported the number of alcoholic beverages consumed (past 30 days) and the number of binge-drinking episodes.
[Results]: Every one-point increase in IQ score was associated with a 1.6% increase in the likelihood of reporting moderate or heavy drinking as compared to abstinence. Those with higher IQ scores also had significantly fewer binge-drinking episodes. Household income, but not education, partially mediated the relationship between IQ and drinking pattern.
The authors do not offer any form of explanation for their observation — they simply present their results as an important form of forecasting an older behavior from a younger characteristic.

Now, I do not actually question the conclusion here. However, I do note that this is not a proper scientific experiment, in the sense that an opportunity was simply taken to collect some data from a group of people:
The initial purpose of the WLS was to gauge the intentions and aspirations of graduating Wisconsin high-school seniors (n = 10,317) regarding their level of post-high-school education, career, and relationships. During the students’ senior year in high school, participants were asked to provide information about the emotional and financial support available to them in pursuit of these goals ... The 90-item, 30-minute Henmon-Nelson Test of Mental Ability was administered to measure spatial, verbal, and mathematical intelligence.
In 1992, an alcohol use module was added to the WLS and administered to a random 80% sample of the original cohort (n = 8,254), which asked participants about the number of drinks consumed, and the number of times having consumed five or more drinks on one occasion, in the prior 30 days. Participants included in the current study were those from the random 80% sample that responded to alcohol use questions during the 2004 measurement wave (n = 6,300), had complete outcomes data, and reported no history of liver disease.
So, an opportunity was taken to collect the IQ data and another opportunity was taken to collect the alcohol data. Furthermore, only those people who responded were included, and there may be some particular reasons why the other people did not respond. The people sampled are also not necessarily representative of most people:
Participants almost exclusively identified as non-Hispanic White and were all born between 1938 and 1940.
As a professional scientist I recognize that this is not the best situation, but it is often the best that can be done in the social sciences (ie. working with humans).

"Safe" levels of alcohol consumption, from the Lancet..

So, what do we make of this? The authors conclude:
As IQ increases, one has a higher likelihood of being either a moderate or heavy drinker as opposed to an abstainer ... Men also had a higher likelihood than women of being either a moderate drinker or heavy drinker relative to being an abstainer ... Income, but not education, was a partial mediator of this relationship.
The data look like this, regarding the number of people in the different groups:
                    Study sample       Abstainer         Moderate          Heavy
    Male        2,912 (46.2%)       724 (24.9%)    1,948 (66.9%)    240 (8.2%)
    Female    3,388 (53.8%)    1,159 (34.2%)    2,004 (59.1%)    225 (6.6%)
That is, a quarter of the men were abstainers and two-thirds were moderate drinkers, and a third of the women were abstainers while three-fifths were moderate drinkers. The gender bias of the participants is not ideal.

Furthermore, the IQ test used may also not be the best. The Henmon-Nelson Test had a major revision in 1961 (4 years after the WLS, when the participants would have left college), and it is reported to now be “a much better measure of general scholastic ability than earlier versions” (Test reviews).

This study was reported in Psychopharmacology, a news aggregation site (High school IQ predicts alcohol use patterns in midlife, study finds), as well as in ScienceAlert (Your IQ in high school can predict your alcohol use later in life). They do not question the study; and you can read their summaries if you do not want to read the original paper.

IQ test ranges.

Health and its relation to intelligence has been a popular topic. It is discussed further in IQ and health: exploring the intricate connection between intelligence and well-being. In particular, these authors note:
Intelligence Quotient, or IQ, is not just a single, static number that defines our mental capabilities. Rather, it’s a complex measure that encompasses various cognitive skills, including logical reasoning, problem-solving abilities, and spatial awareness. Think of it as a Swiss Army knife for your brain — a versatile tool with multiple functions that can be applied to various aspects of life, including our health.
So, there are lots of other research papers to consult. For example: