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Alcohol dependence with comorbid drug dependence: genetic and phenotypic associations suggest a more severe form of the disorder with stronger genetic contribution to risk *
Author(s) -
Dick Danielle M.,
Agrawal Arpana,
Wang Jen C.,
Hinrichs Anthony,
Bertelsen Sarah,
Bucholz Kathleen K.,
Schuckit Marc,
Kramer John,
Nurnberger John,
Tischfield Jay,
Edenberg Howard J.,
Goate Alison,
Bierut Laura J.
Publication year - 2007
Publication title -
addiction
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.424
H-Index - 193
eISSN - 1360-0443
pISSN - 0965-2140
DOI - 10.1111/j.1360-0443.2007.01871.x
Subject(s) - alcohol dependence , drug , substance dependence , phenotype , comorbidity , alcohol use disorder , psychology , addiction , psychiatry , medicine , clinical psychology , alcohol , genetics , biology , gene , biochemistry
Background Twin data suggest that alcohol dependence comorbid with illicit drug dependence represents a more heritable form of the disorder. In the Collaborative Study on the Genetics of Alcoholism sample, approximately half the alcohol‐dependent individuals also meet diagnostic criteria for illicit drug dependence. In this study, we tested for heterogeneity in the association between the muscarinic acetylcholine M2 receptor gene ( CHRM2 ) and alcohol dependence, reported previously in the full sample, among the subgroups of alcohol‐dependent individuals with and without comorbid drug dependence. Methods Family‐based association tests were conducted separately (a) in individuals with alcohol dependence with comorbid drug dependence ( n = 477) and (b) in individuals with alcohol dependence without comorbid drug dependence ( n = 433). These subgroups were subsequently compared on other phenotypic characteristics. Results The evidence for association between CHRM2 and alcohol dependence came entirely from the subgroup of individuals with comorbid drug dependence. There was no evidence of association with CHRM2 among the alcohol‐dependent individuals without drug dependence. Subsequent phenotypic analyses suggest that the subgroup of alcohol‐dependent individuals with comorbid drug dependence differ on a number of other phenotypic characteristics, including several measures of the severity of their alcohol problems, personality traits and comorbid psychiatric disorders. Conclusions These analyses provide specific genetic evidence suggesting that alcohol dependence with comorbid drug dependence represents a particularly severe form of the disorder, with higher genetic contribution to vulnerability.