A genome-wide scan for loci influencing adolescent cannabis dependence symptoms: evidence for linkage on chromosomes 3 and 9.
OBJECTIVE
Cannabis is the most frequently abused illicit substance among adolescents and young adults. Genetic risk factors account for part of the variation in the development of cannabis dependence symptoms; however, no linkage studies have been performed for cannabis dependence symptoms. This study aimed to identify such loci.


METHODS
Three hundred and twenty-four sibling pairs from 192 families were assessed for cannabis dependence symptoms. Probands (13-19 years of age) were recruited from consecutive admissions to substance abuse treatment facilities. The siblings of the probands ranged in age from 12 to 25 years. A community-based sample of 4843 adolescents and young adults was utilized to define an age- and sex-corrected index of cannabis dependence vulnerability. DSM-IV cannabis dependence symptoms were assessed in youth and their family members with the Composite International Diagnostic Instrument-Substance Abuse Module. Siblings and parents were genotyped for 374 microsatellite markers distributed across the 22 autosomes (average inter-marker distance=9.2cM). Cannabis dependence symptoms were analyzed using Merlin-regress, a regression-based method that is robust to sample selection.


RESULTS
Evidence for suggestive linkage was found on chromosome 3q21 near marker D3S1267 (LOD=2.61), and on chromosome 9q34 near marker D9S1826 (LOD=2.57).


CONCLUSIONS
This is the first reported linkage study of cannabis dependence symptoms. Other reports of linkage regions for illicit substance dependence have been reported near 3q21, suggesting that this region may contain a quantitative trait loci influencing cannabis dependence and other substance use disorders.
Hopfer
Christian J
CJ
Division of Substance Dependence, University of Colorado School of Medicine, 4200 East Ninth Avenue, Denver, CO 80262, USA. christian.hopfer@uchsc.edu
Lessem
Jeffrey M
JM
Hartman
Christie A
CA
Stallings
Michael C
MC
Cherny
Stacey S
SS
Corley
Robin P
RP
Hewitt
John K
JK
Krauter
Kenneth S
KS
Mikulich-Gilbertson
Susan K
SK
Rhee
Soo Hyun
SH
Smolen
Andrew
A
Young
Susan E
SE
Crowley
Thomas J
TJ
D000293:Adolescent; D000987:Antisocial Personality Disorder / Q000235:genetics; D002893:Chromosomes, Human, Pair 3 / Q000235:genetics*; D002899:Chromosomes, Human, Pair 9 / Q000235:genetics*; D004200:Diseases in Twins / Q000235:genetics; D005260:Female; D008040:Genetic Linkage / Q000235:genetics*; D005819:Genetic Markers / Q000235:genetics; D016678:Genome; D005838:Genotype; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000235:genetics*; D018895:Microsatellite Repeats; D012044:Regression Analysis
D005819:Genetic Markers