Found this on mayoclinic.com site.
In my search to find the right antidepressent, trawling through posts on boards etc. etc. I found this: Anyone heard of it??
Blood test may help in choosing antidepressants
A blood test may help make the antidepressant decision somewhat easier. The test, called the cytochrome P450, helps pinpoint genetic factors that influence your response to certain antidepressants (as well as some other medications). The test doesn’t predict which antidepressant will work best for you. But it does help suggest which ones may not work, and which ones may have the greatest side effects specifically for you.
Although they may be a good first step in personalized medicine, genotyping tests have limitations. One is that they can’t predict if certain medications will actually work — they can only show which probably won’t work. In addition, the CYP450 test only looks at some of the genes involved in metabolizing drugs. Not all antidepressants are processed by these genes. Those that are included:
Paroxetine (Paxil, Paxil CR)
Finally, genotyping tests aren’t yet available in all communities nor do all doctors use them. And some health insurance plans don’t cover the tests, so check with your health insurance provider. If you opt for testing, keep in mind that the CYP450 genotyping test isn’t meant to be the only way to determine which antidepressants to try. A thorough medical and psychiatric evaluation, as well as consideration of your preferences and lifestyle, is equally important.
There is more about it on mayoclinic.com