In a well-known paper in schizophrenia research, Timothy Crow argues that schizophrenia is the price Homo Sapiens pay for having language. In a way, this makes sense. Think of any organism or machine. The more parts they have, the more complex they are, the more things can go awry.
On this view, it could be argued that you should thank a person with schizophrenia (if you are not so diagnosed) because they are evidence of your complexity–in addition to having a complexity of their own!
The features of schizophrenia may seem odd or unusual to those not so diagnosed, but they are really just things that are magnified that you probably experience–an eerie feeling, seeing a shadow and thinking something is there. These are things many people experience but that are more pronounced in people with schizophrenia.
I do not know whether schizophrenia is the price we pay for having language, but it’s worth a thought or two.