In mice, the genetic locus best correlated to anxiety-related behaviour contains the 'regulator of G protein signaling 2' gene [anxiety related disorders.[PMID 18316676]
In the first part of one study, 119 families including children underwent standard lab-based behavioural assessments of behavioural inhibition, defined as a heritable temperamental profile characterized by a tendency to be shy, avoident, and behaviourally restrained in situations that are novel or unfamiliar. Along with some other RGS2 SNPs, carriers of a rs4606(G) allele were 3 fold more likely to exhibit behavioural inhibition (CI: 1.31-6.84, p = 0.0026).
In the second part of this study, 744 college undergraduates (228 men, 516 women) who had been genotyped completed a personality profile known as the NEO-E (introversion) association test. Consistent with the earlier results, the same RGS2 alleles associated with behavioural inhibition were significantly (p < 0.05) associated with introversion (but not neuroticism), including rs4606(G), rs6428136(G), and rs10801152(T).
In the third part of this study, 55 female undergraduates were studied by fMRI (functional MRI) emotional processing tests. Carriers of SNPs rs4606(G) or rs10801152(T) showed increased insular cortex activation, a reflection of anxiety, in these tests.
Based on these results, the authors predict that social anxiety disorder is the most likely anxiety disorder to be associated with SNPs in the RGS2 gene such as rs4606.
[PMID 18316676] SNPs in the RGS2 gene, including rs4606, show association with childhood temperament, adult personality, and brain function.
[PMID 18833580] each rs4606(C) allele was associated with a 2x (p =.026) increased risk of generalized anxiety disorder.
[PMID 16736243] 173 patients with panic disorder (and 173 matched controls) of German descent analyzed, leading to the conclusion that rs4606(G) carriers were at ~2x increased risk for this disorder. Note that the (G) allele appears to be the minor (rarer) allele in this study.
Note: given the conflicting reports over whether the (C) or (G) allele is implicated in anxiety-related disorders, Dr. Jordan Smoller was contacted to verify that the orientation was unambiguously reported in the various publications. He has confirmed that the reports truly vary in which allele is considered the risk allele; this may be an example of the "flip-flop" phenomenon [PMID 17273975].
rs4606 has also been reported to be associated with the development of Parkinson's like symptoms in schizophrenia patients treated with various drugs, as follows:
[PMID 18347610] A replication study was performed in which extrapyramidal symptoms (EPS) were rated in 184 US patients with schizophrenia. This group (115 African Americans, 69 Caucasian) was treated for at least a month with typical antipsychotic drugs (n=45), risperidone (n=46), olanzapine (n=50) or clozapine (n=43). The minor (G) allele showed a protective effect against antipsychotic-induced parkinsonism (AIP), with an odds ratio for AIP among rs4606(G) carriers of 0.23 (CI: 0.10-0.54, p=0.001) for the overall sample.