Non-response to antidepressants is one of the major problems in mental health (see post below). Only about half of adult patients respond to the first antidepressant they try, with only a third achieving remission. Patients can either switch to a new drug altogether or augment the first drug with another one although it is not clear which of these strategies is the more effective. The Sequenced Treatment Alternatives to Relieve Depression (STAR*D) study is the largest study into this issue ever undertaken and has found that both options are equally effective. The study also found that with persistent trial and error 7 out of 10 adult patients will eventually find a treatment that works.
You can find out more about this research at