Similarly, variants in GABBR2 (on chromosome 9q22), which encodes the GABAB receptor subunit 2, have been associated with ND.28 Linkage of chromosome 9 with smoking behavior has been reported in several independent studies,29–32 and GABBR2 contributes 28%–38% to this linkage signal.33 The involvement of GABA signaling across addictions has been confirmed in animal models (see below).
