From what understand, this is an emerging field, with more unknown than known. Some genes correlated with antidepressants are those involved with the metabolism of the medications. With that info, the Dr can try meds for best potential effect and least toxicity/ side effects. Some genes are correlated with depression itself. Gosh I have a lot to learn. Thanks for inspiring the search to learn. I searched genes and antidepressant medications. here are a few:
Influence of 5-HTR2A genetic polymorphisms on the efficacy of antid... - PubMed - NCBI
Genetics and personalized medicine in antidepressant treatment. - PubMed - NCBI
Tracking genes that up suicide risk with antidepressant use | Genetic Literacy Project