Chunk #19 — Identifying Specific Genes Related to AOD Dependence — Genes Encoding Proteins Involved in Neurotransmission — Genes Encoding the GABAA Receptor
Variations in the GABRA2 gene are associated not only with AOD dependence but also with certain electrophysiological characteristics (i.e., endophenotypes) in the COGA sample (Edenberg et al. 2004). As reviewed above, these electrophysiological characteristics are not unique to alcohol dependence but also are found in individuals with other forms of externalizing psychopathology. This association supports the hypothesis that the GABRA2 gene generally is involved in AOD use and/or externalizing problems. Interestingly, subsequent analyses investigating the role of GABRA2 in drug dependence (Agrawal et al. 2006) found that the association with GABRA2 was strongest in people with co-morbid AOD dependence, with no evidence of association in people who were only alcohol dependent. This observation supports the assertion that co-morbid AOD dependence may represent a more severe, genetically influenced form of the disorder.
