Will it be necessary for me to try more than one antidepressant?

This all depends on how good you and your psychiatrist are at selecting antidepressants. With a good doctor-patient relationship, good information, and some luck, you will find the best antidepressant on the first try. Then it is just a matter of finding the perfect dose and adjusting it over the course of weeks or months. If you are not happy with the results or you find that there are still depressive problems left after you have reached your highest dose, then you may need to change your treatment strategy.