The ADRA2B gene encodes subtype B of the α2-adrenergic receptor, which influences norepinephrine activity, and it is a member of the G-protein coupled receptor family.Wikipedia
A deletion variant (deleting three glutamic acids; residues 301–303; see below) of the α2B adrenergic receptor has been shown in a study of ~400 participants to be related to emotional memory in Europeans and Africans. This variant is relatively common in Caucasians but less common in other ethnicities.[PMID 17660814]
In October 2013 a relatively small study (of ~200 people) concluded that this deletion variant predisposes carriers to greater vigilance, or to put it another way, to focus more on the negative aspects of a situation.[PMID 24058067]
Due to the repeating nature of the nucleotides encoding the stretch of glutamic acid residues in this part of the ADRA2B gene, the numbering of the exact location of this variant is problematic. The SNPs that equally correspond to this variant include rs28365031, rs29000568, and rs4066772.