This approach may work in other fields, notably oncology, though with a very low success rate. However psychiatric disorders are not fully understood. You can attempt to normalize abnormal levels of neurotransmitters which is what many psychiatric medications do, but that can only go so far, and it is going to have many off target effects. It's also much more difficult to try such a brute force trial and error approach since you can't simplify the brain into cheaper models. In oncology you can grow tumor cells in petri dishes and throw every chemical you can find at them to see what happens, it's expensive but not nearly as expensive as doing the same in vivo.