Transcript Comings et al. (1996)

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:
 222 pathological gamblers diagnosed
according to the DSM-IV (1994) criteria for
pathological gambling
 714 controls screened to exclude drug and
alcohol abuse.
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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
N
Prevalence
of D2A1
Frequency
of 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%
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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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