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Family studies have found that gambling problems are more common among relatives of people with gambling problems. These studies provide some evidence to support the genetic inheritance of harmful gambling. However, family studies cannot answer to what extent gambling is shaped by genetics as compared to the environment.
Twin studies are the gold standard design to understand the influences of genetics versus the environment. These studies compare identical twins and non-identical twins. Identical twins share nearly all of their genetic makeup, whereas non-identical twins share about half of their genetic makeup. Twin studies have revealed that genetic factors account for about 50% of the chance of developing gambling problems; but, most twin studies have been based on male twin pairs and included participants who might not have been diagnosed by a clinician.
Gambling can be modified by the environment; some twin studies have examined the effects of shared and non-shared environmental factors. Shared environmental factors are features of the environment that are common to both twins, such as their upbringing and the neighbourhood in which the family lives. Non-shared environmental factors are unique to each twin, such as friends that one has. There is typically a strong role of non-shared environmental factors on gambling, with only a minor role of shared environmental factors. Recent studies have considered both genetic and environmental influences. It has been reported that genetic influence on gambling is greater among people living in disadvantaged neighbourhoods.
Recent studies have also attempted to identify specific genes that contribute to harmful gambling. Some studies have tested for variants in genes affecting dopamine release in the brain. Dopamine is a neurotransmitter (i.e., a chemical in the brain) that plays an important role in various functions, including motor control, reward response, and learning. Yet, most studies have been small studies with few participants, and there have been failures to replicate the same results in different studies. Overall, it appears that the development of harmful gambling is shaped by many genes and the environment.
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Download the Biological Factors section from the Conceptual Framework of Harmful Gambling (PDF)
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