Table 2 Epidemiologic studies of dopamine receptor gene (DRD2), dopamine transporter gene (SLC6A3) and tobacco use in human populations.

Erblich 2004

USA N = 108 smokers

SLC6A3-9/*^avs. 10/10

SLC6A3-9/* increases number of cigarettes/day

DRD2 A1/*^avs. A2/A2

SLC6A3-9/* & DRD2 A1/* exhibit greater cigarette craving reactions

Additive interaction of both gene variants

Vandenbergh 2002

USA N = 595

SLC6A3-10/10, 9/10, 9/9

SLC6A3-9/* predicts increased smoking^b

Yoshida 2001

Japan N = 332

DRD2 A1/A1, A1/A2, A2/A2

A2 predicts increased smoking

Wu 2000

USA N = 140 lung cancer cases and 222 controls

DRD2 A1/A1, A1/A2, A2/A2

DRD2 predicts increased smoking, pack-years and number of cigarettes/day

DRD2 B1/B1, B1/B2, B2/B2

A1 & case status interact to increase risk of family history of smoking-related cancer

Beirut 2000

USA N = 970 Alcoholism study subjects and their first-degree relatives

DRD2 A1/* vs. A2/A2

No significant differences by genotype

Lerman 1999

USA N = 522

DRD2 A1/* vs. A2/A2

SLC6A3-9/* predicts non-smoking, older age at initiation of smoking, and longer previous quit attempts

SLC6A3-9/* vs. */*

DRD2-A1/* predicts smoking only through interaction with SLC6A3

Sabol 1999

USA N = 1,107

SLC6A3-9/* vs. */*

SLC6A3-9/* predicts smoking cessation & low novelty-seeking

DRD2 A1/* vs. A2/A2

Spitz 1998

USA N = 283

DRD2 A1/* vs. A2/A2

DRD2 A1/* or B1/* predict increased smoking, younger age at initiation & fewer attempts to quit

DRD2 B1/* vs. B2/B2

Comings 1996

USA N = 1026 (479 of which are from literature)

DRD2 A1/* vs. */*

DRD2 A1/* predicts smoking

Noble 1994

USA N = 354

DRD2 A1/* vs. A2/A2

DRD2 A1/* predicts increased smoking

Smith 1992

USA N = 232

DRD2 A1/* vs. A2/A2

DRD2 A1/* or B1/* predict increased substance use

DRD2 B1/* vs. B2/B2