The first answer is too vague to have a meaningful answer in case.
Every other treatment in medicine including schizophrenia is tested how it works in practice. It is incurable disease and the treatments have many side-effects. Thus the question becomes not “does this medicine cure schizophrenia” but “does this treatment works better than placebo or another treatment?”. When studies are completed, we gather evidence by monitoring real life experience with this treatment.
Every other treatment in medicine including schizophrenia is tested how it works in practice. It is incurable disease and the treatments have many side-effects. Thus the question becomes not “does this medicine cure schizophrenia” but “does this treatment works better than placebo or another treatment?”. When studies are completed, we gather evidence by monitoring real life experience with this treatment.