Chromosome 20 shows linkage with DSM-IV nicotine dependence in Finnish adult smokers.
BACKGROUND
Chromosome 20 has previously been associated with nicotine dependence (ND) and smoking cessation. Our aim was to replicate and extend these findings.


METHODS
First, a total of 759 subjects belonging to 206 Finnish families were genotyped with 18 microsatellite markers residing on chromosome 20, in order to replicate previous linkage findings. Then, the replication data were combined to an existing whole-genome linkage data resulting in a total of 1,302 genotyped subjects from 357 families. ND diagnosed by DSM-IV criteria, the Fagerström Test for Nicotine Dependence (FTND) score, and the lifetime maximum number of cigarettes smoked within a 24-hr period (MaxCigs24) were used as phenotypes in the nonparametric linkage analyses.


RESULTS
We replicated previously reported linkage to DSM-IV ND, with a maximum logarithm of odd (LOD) score of 3.8 on 20p11, with females contributing more (maximum LOD [MLOD] score 3.4 on 20q11) than males (MLOD score 2.6 on 20p11). With the combined sample, a suggestive LOD score of 2.3 was observed for DSM-IV ND on 20p11. Sex-specific analyses revealed that the signal was driven by females with a maximum LOD score of 3.3 (on 20q11) versus LOD score of 1.3 in males (on 20q13) in the combined sample. No significant linkage signals were obtained for FTND or MaxCigs24.


CONCLUSIONS
Our results provide further evidence that chromosome 20 harbors genetic variants influencing ND in adult smokers.
Corresponding Author: Jaakko Kaprio, M.D., Ph.D., Department of Public Health, University of Helsinki, PO Box 41 (Mannerheimintie 172), Helsinki 00014, Finland.
Kaisu
K
Keskitalo-Vuokko
Jenni
J
Hällfors
Ulla
U
Broms
Michele L
ML
Pergadia
Scott F
SF
Saccone
Anu
A
Loukola
Pamela A F
PA
Madden
Jaakko
J
Kaprio
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000483:Alleles; D002890:Chromosomes, Human, Pair 20 / Q000235:genetics*; D003627:Data Interpretation, Statistical; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D005387:Finland / Q000453:epidemiology; D008040:Genetic Linkage; D020022:Genetic Predisposition to Disease; D005838:Genotype; D006801:Humans; D008126:Lod Score; D008297:Male; D018895:Microsatellite Repeats; D008875:Middle Aged; D010641:Phenotype; D012737:Sex Factors; D012907:Smoking / Q000235:genetics*; D016540:Smoking Cessation; D013997:Time Factors; D014029:Tobacco Use Disorder / Q000453:epidemiology / Q000235:genetics*; D044465:White People / Q000235:genetics*