How intelligence and education contribute to substance use: Hints from the Minnesota Twin family study

Abstract

In old and even middle age, there are associations between physical health and both intelligence and education. This may occur because intelligence and/or education exert effects on lifestyle choices that, in turn, affect later health. Substance use is one aspect of lifestyle choice in young adulthood that could play such a role. The effects of intelligence and/or education on substance use could be direct and environmental, or indirect due to the presence of confounding genetic and shared family influences. We used the Minnesota Twin Family Study to distinguish these effects in males and females at age 24. In contrast to prevailing expectations, there were moderately negative direct nonshared environmental effects of both IQ and education on both smoking and drinking in both males and females. That is, controlling for positive family background effects in the form of both genetic and shared environmental influences, both higher IQ and greater education were associated with greater alcohol and nicotine use. These effects were accounted for by alcohol and nicotine use at age 17. Our results suggest that genetic and family-culture variables confound the associations between intelligence and education and substance use in young adults, rendering them indirect. Further research is needed to understand the roles of IQ and education in alcohol and nicotine use and their relative impacts on physical health throughout the lifespan. KeywordsIQ; education; health-related behaviors; alcohol use; smoking; substance use; young adulthood In middle and old age, there are associations between physical health and both intelligence and education (Carlson, Fried, Ave, Bandeen-Roche, Zeger, & Brandt, 1999;Deary, Whalley, Batty, & Starr, 2006;Gottfredson & Deary, 2004;Malmstrom, Wolinsky, Andresen, Miller, & Miller, 2005;Tabbarah, Crimmins, & Seeman, 2002), but how these associations develop is not understood. Physical health problems are major sources of economic expense, anxiety, and deterioration in quality of life. Understanding the ways in which intelligence and education contribute to physical health would be an important epidemiological advance, and might lead to new approaches to help people better manage their own health, leading to more effective disease prevention and reduced medical care costs.One possible reason for the associations between physical health and intelligence and education is that intelligence and/or education may act to support lifestyle choices and the development of habits that over time maintain or undermine physical health. Education is generally the Corresponding author: Wendy Johnson, c/o Department of Psychology, University of Minnesota -Twin Cities, 75 East River Road, Minneapolis, MN 55455, 952-473-1673, wendy.Johnson@ed.ac.uk. NIH Public Access Author ManuscriptIntelligence. Author manuscript; available in PMC 2010 November 1. Published in final edited form as:Intelligence. 2009 November 1; 37(6): 613-624. doi:10.1016/j.intell.2008.12.003. NIH-PA Author ManuscriptNIH-PA Author Manusc...

Intelligence and Substance Use

“…The measures of substance consumption that we use in Study 1 reflect NCDS respondents' behavior throughout their adulthood in their 20s, 30s, and 40s, whereas those that we use in Study 2 reflect Add Health respondents' behavior in their early adulthood in their 20s. Note that previous studies of American samples find a positive effect of intelligence on smoking (Johnson et al, 2009), while those of British samples find a negative effect Batty, Deary, & Macintyre, 2007). So this appears to be a consistent and replicable national difference between the United States and the United Kingdom.…”

“…Similarly, a behavior genetic analysis of twin pairs from the Minnesota Twin Family Study shows that, controlling for genetic and shared environmental influences, men and women with higher IQ at age 17 are more likely to use alcohol at age 24 (Johnson, Hicks, McGue, & Iacono, 2009).…”

IQ and Level of Alcohol Consumption—Findings from a National Survey of Swedish Conscripts

“…It should be noted that the authors report a skewed study population with regard to low socioeconomic position (Windle and Blane, 1989). Another twin study from the United States, found a positive association between IQ test results at age 17 and an alcohol use composite, where, for example, symptoms of alcohol abuse/dependence and average quantity consumed in the past 12 months were considered (Johnson et al., 2009). …”

“…The scientific literature on intelligence and alcohol consumption in adolescence, measured as total intake and type of drinking, is scarce. A twin study from the United States showed that a high IQ assessed at age 17 was associated with heavier alcohol use as measured by an alcohol use composite, taking into account symptoms of alcohol abuse/dependence, number of intoxications, frequency of use and number of drinks during a year, and maximum number of drinks within 24 hours (Johnson et al., 2009). A study from Switzerland investigated how IQ test results from conscription were associated with frequency of drinking, defined as nondrinking, rare drinking (1 to 5 times/y), occasional drinking (1 to 5 times/month), moderate drinking (1 to 5 times/wk), and daily drinking.…”

9 Executive Function and Intelligence in the Development of Antisocial Behavior

“…However, the main challenge to that assumption is that, at least in adolescence, obtaining access to substances has been associated with higher cognitive abilities (Castellanos-Ryan, Johnson, Hicks, McGue, & Iacono, 2009;White & Batty, 2012). Cognitive abilities are therefore construed as providing an advantage for accessing resources, such as substances which have several motivational properties (Hyman, Malenka, & Nestler, 2006).…”