Gambling Addiction: The Sensible Years, Studied In Twins

For some young people, the transition to adulthood also means starting a career as a gambler. Researchers have discovered that genes are also involved.

In the beginning, it is the profit and the powerful feeling of having defeated the machine, the computer, or the bank. In the end, however, nothing remains but a mountain of debt and pure despair. For between 1 and 5% of the general population, gambling has become a drug (1).

If one adds the problematic players, those who are about to slide into an addiction, one quickly exceeds millions in many countries. The transition from youth to young adulthood seems to be an especially sensitive time, as the number of people affected at that age increases noticeably. But why is that? Is it the influence of friends, or do genes play the decisive role? To find out, American researchers led by Serena King (2) evaluated the data of 756 pairs of twins from Minnesota. All siblings were between 18 and 25 years old, i.e. in that critical transition phase between adolescence and adulthood.

According to the researchers’ calculations, the influence of genes on play behavior rose from 21 percent to 57 percent during this period. The influence of the genetic material can thus be quantified precisely because the test persons in such studies are mostly twins. Their genetic makeup is either almost completely identical (identical twins) or half identical (fraternal twins). If monozygotic twins are more similar in their play behavior than fraternal twins, this must be largely due to the genes.

In this study, the researchers found out how often the test persons played, what was the largest amount they ever gambled away and what signs of addiction they might have already shown, with the help of questionnaires. Around 68 percent of the test persons had tried their luck at least once at the age of 18. At 25, the figure was 76 percent. However, the researchers were unable to observe any addictive behavior in their twin group. In addition, the money that the adolescents and young adults gambled away on a maximum of one day was on average not much higher than two dollars. However, the order of magnitude that the researchers calculated for the influence of genes fits in with another study which assumes that the differences in playing behavior in adolescents can be explained by the genes to about 32 percent (3).

In addition to the influence of genes, King and her colleagues were also interested in the role of the environment for young people and young adults. Here, they observed the opposite trend. Influences shared by the twin siblings, such as experiences in the family, only had a greater influence on the 18-year-olds. Within seven years, the effect fell from 55 to 10 percent. Individual environmental factors, such as friendships, also played a role, but far less so than other factors.

The researchers now hope that research in this field will continue. If the genes and environmental influences that influence young people’s playing behavior could be identified, it might be possible to prevent pathological player careers.

This is part 29 of a series covering twin health provided by Paul Enck from the Tübingen University Hospital and science writer Nicole Simon. Further studies in twin research can be found at TwinHealth website. Translation was done with the assistance of DeepL translator.


  1. Calado F, Griffiths MD. Problem gambling worldwide: An update and systematic review of empirical research (2000-2015). J Behav Addict. 2016 Dec;5(4):592-613.
  2. King SM, Keyes M, Winters KC, McGue M, Iacono WG. Genetic and environmental origins of gambling behaviors from ages 18 to 25: A longitudinal twin family study. Psychol Addict Behav. 2017;31(3):367-374.
  3. Blanco C, Myers J, Kendler KS. Gambling, disordered gambling and their association with major depression and substance use: A web-based cohort and twin-sibling study. Psychological Medicine 2012; 42; 497–508.