No association between the dopamine d2 receptor taqi a1 allele and earlier age of onset of alcohol dependence according to different specified criteria.
BACKGROUND
The presence of the A1 allele of the dopamine D2 receptor TaqI restriction fragment length polymorphism has been reported to be associated with an earlier age of onset of alcohol dependence as a marker for severity.


METHODS
We tested this hypothesis with special regard to the definition of the age of onset of alcoholism in 243 patients with alcohol dependence, according to DSM-IV criteria assessed by the standardized interview Münchner Composite International Diagnostic Interview (M-CIDI), consecutively admitted for detoxification. Additionally, the Addiction Severity Index (ASI) was performed. The TaqIA polymorphism was amplified by polymerase chain reaction (PCR), and the PCR product was digested by the restriction enzyme TaqI. Patients were subsequently divided into an A1 (presence of at least one A1 allele, n = 88) and an A2 group (absence of an A1 allele, n = 155). The following criteria for different definitions of age of onset were used: (1) age of onset of the first occurring symptom necessary for the diagnosis of alcohol dependence according to M-CIDI; (2) age of onset of the last symptom of alcohol dependence according to M-CIDI; (3) age of onset of more than 3 drinking days per week on a regular basis according to ASI; (4) age of onset of more than 3 drinking days-of more than five drinks per drinking day-or at least one binge drinking episode per week on a regular basis according to ASI.


RESULTS
The frequency of the A1 allele in our patient sample was 0.208. No statistically significant association between the A1 allele and the age of onset of alcoholism was found. The mean age of onset according to criterion 1 was 30.4 +/- 10.8 years for the A1 group and 30.2 +/- 10.2 years for the A2 group (p = 0.89); for criterion 2, it was 33.3 +/- 10.0 years for the A1 group and 33.9 +/- 10.2 years for the A2 group (p = 0.77); for criterion 3, it was 18.0 +/- 7.5 years for the A1 group and 18.1 +/- 6.1 years for the A2 group (p = 0.92); and for criterion 4, it was 22.3 +/- 9.7 years for the A1 group and 21.8 +/- 8.5 years for the A2 group (p = 0.76).


CONCLUSIONS
No association was found between the A1 polymorphism and age at onset of alcohol dependence according to different specified criteria.
Anghelescu
I
I
Department of Psychiatry, University of Mainz, Untere Zahlbacher Str. 8, 55131 Mainz, Germany. anghelescu@mail.psychiatrie.klinik.uni-mainz.de
Germeyer
S
S
Müller
M J
MJ
Klawe
C
C
Singer
P
P
Dahmen
N
N
Wetzel
H
H
Himmerich
H
H
Szegedi
A
A
D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000437:Alcoholism / Q000175:diagnosis / Q000235:genetics*; D000483:Alleles; D005260:Female; D005787:Gene Frequency; D006801:Humans; D008297:Male; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D017448:Receptors, Dopamine D2 / Q000235:genetics*; D019914:Taq Polymerase; D014029:Tobacco Use Disorder
D017448:Receptors, Dopamine D2; D019914:Taq Polymerase