Opportunities to gamble have increased starkly over the last 50 years, and with it has come a shift in social attitude towards gambling. Wendy Slutske, PhD, recipient of a 2017 NCRG Center of Excellence Grant, set out to compare the role of genetics and environment from two National Twin Studies, collected about 50 years apart, on propensity to gamble.
What is the aim?
The aim of this study by Slutske, (2018), was to examine the difference in genetic and environmental factor contribution and overall prevalence of gambling involvement in the United States in 1962 versus 2002. It was hypothesized that both prevalence and heritability of gambling would be higher in 2002 than 1962 due to various social factors and the expansion of legalized gambling.
What did the researchers do?
The researcher completed a secondary analysis on the gambling propensity data of two national samples of young twins from National Merit Scholarship Qualifying Test twin study (National Merit) and National Longitudinal Study of Adolescent to Adult Health (Add Health). The National Merit Study data was ascertained in 1962 from a sample of high school juniors that completed the National Merit Scholarship test and included 509 MZ twin pairs and 330 DZ twin pairs of an average 17 years of age. National Longitudinal (Add Health) data was ascertained in 2001-2002 from a sample of adolescents and young adults and included 220 MZ twins, and 182 DZ twins from 45 different states. Both studies included assessments of participation in gambling at the time, categorized into yes/no responses to various gambling activities. The considerable overlap in the two assessments allowed the researcher to compare prevalence of gambling activity and use a statistical model to compare the influence of genetic and environmental influences in gambling participation.
Why is this important
Twin studies are important to public health because they allow researchers to look at the comparative influences of genetics and environment on a certain behavior. This study is modeled after previously completed cigarette studies; which looked at the influence of social factors on smoking behavior. These found that as the social acceptability of smoking increased, prevalence and genetic heritability increased as well (Kendler et al., 2000; Mezquita et al. 2018). This present gambling propensity study set out to find whether gambling followed this same pattern of increased heritability and prevalence with increased social acceptance.
What did they find
Prevalence: The researcher found the prevalence of gambling activity (yes/no) of the 2002 Add Health full sample to be significantly greater than the 1962 National Merit full sample (75% versus 49%, with an odds ratio of 2.80, p
Genetic and Environmental Propensity: The researcher found there to be no difference in genetic contribution to gambling propensity between the two cohorts. It was also determined that all the variation in propensity to gamble in both cohorts was due to environmental factors, including both shared factors between twins, and factors that are unique to the individual.
Overall: The researcher was surprised by these genetic and environmental factors contribution to gambling propensity. She had hypothesized that genetic heritability would differ between the two cohorts, but this study proved that incorrect. The author offered that this could be due to environmental cross-state differences that existed in both 1962 and 2002.
Limitations
The first obvious limitation of this sample was that the ages of the samples differed, with National Merit participants all approximately 17 years old, and Add Health participants 18-26 years old. In addition, secondary analyses on previously obtained data hold inherent limitations, such as vulnerability to changing definitions, unknown confounders, and unknown effect of biases.
References
Slutske, W. S. (2018). Has the genetic contribution to the propensity to gamble increased? Evidence from national twin studies conducted in 1962 and 2002. Twin Research and Human Genetics, 21(02), 119-125. doi:10.1017/thg.2018.7
Kendler, K. S., Thornton, L. M., & Pedersen, N. L. (2000). Tobacco consumption in Swedish twins reared apart and reared together. Archives of General Psychiatry, 57, 886–892.
Mezquita, L., Sánchez-Romera, J. F., Ibáñez, M. I., Morosoli, J. J., Colodro-Conde, L., Ortet, G., & Ordoñana, J. R. (2018). Effects of social attitude change on smoking heritability. Behavior Genetics, 48, 12–21.
