Some studies indicate that this genotype is associated with slightly increased risk for certain mental health disorders; other studies have found no association. [PMID 20682308] [PMID 20087404 ][PMID 20033742] [PMID 19699537] [PMID 18286632] [PMID 15940292] [PMID 20943059] [PMID 19603419] [PMID 18600033]
Also, On a driving-based motor learning task subjects with this genotype showed greater error during short-term learning and poorer retention over 4 days, relative to subjects without the polymorphism. The presence of this BDNF polymorphism is associated with differences in brain motor system function, altered short-term plasticity, and greater error in short-term motor learning. [PMID 19745020]
wiredscience/2009/10/ genetically-bad-driving/ Wired discusses the research as does 10/30/snpwatch-the-bad- driving-gene/ 23andMe blog.