Do you have a source for these claims? Because the DSM-5 says otherwise
>Diagnosis is based on observed behavior, the person's reported experiences, and reports of others familiar with the person...As of 2013 there is no objective test. [5]
Edit: the source you edited in simply states the corollary to what I've been saying all along: that scientists are still searching for a biological test for mental illness but as yet still do not have one
>Diagnosis is based on observed behavior, the person's reported experiences, and reports of others familiar with the person...As of 2013 there is no objective test. [5]
https://en.m.wikipedia.org/wiki/Schizophrenia
Edit: the source you edited in simply states the corollary to what I've been saying all along: that scientists are still searching for a biological test for mental illness but as yet still do not have one