Opioid dependence (OD) is associated with serious medical, legal, and social problems, and co-occurring psychiatric disorders. The cost of OD to society in 2002 was ~$181 billion (1). Although genomewide association study (GWAS) is the method of choice to identify risk genes for complex traits, none has been published for OD, despite an estimated heritability of >0.60 (2). The strongest GWAS-derived noteworthy and replicable genomewide significant (GWS) results so far for drug dependence (DD) traits identified a set of loci mapping to a chromosome 15 nicotinic receptor gene cluster (e.g., ref. (3)) for nicotine dependence (ND) and related traits; we also reported a GWS association of the FAM53B locus to cocaine dependence (CD) (4).
