The D2 Receptor Gene in Gambling

The study of Comings et al. (1996):

Gambling has been defined as an impulse control disorder (DSM-IV, 1994), and has many similarities with alcoholism and substance dependence.

Researchers have found a link between the D2A1 allele gene and drug addiction, some forms of severe alcoholism and other impulsive, addictive behaviors.

A United States study examined whether a similar pattern was associated with pathological gambling.

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The D2 Receptor Gene in Gambling

Participants were 936 non-Hispanic Caucasians, including:

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222 pathological gamblers diagnosed according to the DSM-IV (1994) criteria for pathological gambling

714 controls screened to exclude drug and alcohol abuse.

The D2 Receptor Gene in Gambling

Of the 222 pathological gamblers:

171 contributed blood samples.

102 contributed blood and completed a gambling questionnaire.

Of the 714 controls:

484 of these were obtained from previously published studies.

The remaining 230 were newly tested for the current study.

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The D2 Receptor Gene in Gambling

The genotypes were read from blood samples

by two blind readers.

That is, they were blind as to whether the

participant was a pathological gambler or a

control. This eliminated a bias due to positive

test strategy, that is a bias to incorrectly read

the data in a manner that would support the

hypotheses.

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The D2 Receptor Gene in Gambling

Dependent measures were:

Prevalence of the D2A1 allele: The percentage of

individuals carrying the D2A1/D2A1 or D2A1/D2A2

genotype.

Frequency of the D2A1 allele: The total number of

D2A1 alleles divided by the total number of haploid

sets of chromosomes.

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The D2 Receptor Gene in Gambling

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N Prevalenceof D2A1

Frequencyof D2A1

Controls 714 26% 0.15

Pathological Gamblers 171 51% 0.27

Upper half of gambling score (44) 41%

Lower half of gambling score (58) 64%

The D2 Receptor Gene in Gambling

Both prevalence and frequency were higher in pathological gamblers than in controls.

When the 102 pathological gamblers who had completed the gambling questionnaire were divided according to their gambling scores, those scoring in the upper half had higher prevalence than those scoring in the lower half.

These results suggest that genetic defects in the dopamine receptor gene do play a role in the development of pathological gambling.

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