The statement that they should probably need to be cared for in a mental institution isn't true. That some or several may need to be cared for is true, yes, but the probability of that need is less well know. Schizophrenia and other schizophrenia-related disorders can often 'mellow out' on their own over time. [1] It is important to give someone a stable and loving and validating environment for them to be able to recover. There are several kinds of people who, while they talk to themselves, really just have their symptoms exacerbated by stress (e.g. schizotypal personality disorder can have quasi-psychotic symptoms triggered by stress).
1. https://www.nationalelfservice.net/mental-health/schizophren... (I will also note that this has been anecdotally determined, though I understand anecdotes are not data.)