Well as you can tell, I have been doing some light reading. The bottom line - The current thought is a handful of genes that make people more sensitive to anxiety and/or depression. There is also multiple variation in the genes. So you might be sensitive to, slightly sensitive to or very sensitive to anxiety as an example. Right now most drs are not recommending a genetic testing as there isn't any treatment for abnormal genes only treatment for the symptoms. Those with the most variation in these genes are typically the hardest to treat because they are the most vulnerable to stress and relapse.
http://www.webmd.com...ponse-to-stress
Summarizes research on depression gene.
http://www.psycholog...-disorder-fkbp5
Anxiety Gene
http://www.ncbi.nlm....les/PMC3181835/
Research on anxiety gene.
http://www.livestron...ession-anxiety/
Genes as a factor for anxiety & depression.
http://www.ncbi.nlm....pubmed/23627963
Emotional Gene study on 4 year old children.