My personal readings on.. pretty much this exact subject .. is that there are a handful of effective drugs for specific - easily identifiable - problems and a larger number of drugs that mostly just calm you the heck down, and that misdiagnosis is a really major problem for both effective treatment and the development of treatments.

If you are bi-polar, then any doctor or shrink worth his salt is going to diagnose that correctly, and lithium will help. If you have a problem with a less clear cut set of symptoms? You are going to wind up with a diagnosis. Some diagnosis. Which may, or may not, be even remotely right, but now it is in your medical file, and all further symptoms are read through that filter. It is very rare that a diagnosis gets revised. This in turn makes developing treatments for mental issues a lot harder. When you are trying to develop a cure for a cancer or an infection, the group you test your drugs on will not in fact instead be suffering from fracking lupus. If you are testing a drug or other treatment for any given mental problem? Yhea, if you are really lucky, then half your test group has the actual problem you wish to treat.