Reply #2: Before approval, efficacy must be shown in 2 clinical trials.

[godai]

Clinical trials often fail to show efficacy and they can be repeated and looked at independently. Sometimes, for example, the trial wasn't large enough to show a statistical effect over placebo. When a drug repeatedly fails to indicate efficacy in trials, the drug company will drop it as not effective.

Anti-depressants are effective, with numerous side effects but the new study leads England to conclude that non-drug treatment may be the long term preferred treatment, dropping the drug treatment when the patient is stabilized.