How so? Genuinely trying to understand, as DID was formerly characterized as multiple personality disorder, and the way you describe your friends seem like it would fit (i.e. a dissolved idea of identity).
I know 3-4 people with schizophrenia, and none of them displayed the kind of wild delusions you're describing (though I am not discounting them! Don't get me wrong). In my experience schizophrenia manifests itself more like a worse form of anxiety, paranoia and depression mixed together (all my friends are under treatment and medicated).
As I understand it schizophrenia leads you to make unwarranted connections between things, and then the mind tries to give an explanation. There's no dissolved idea of identity in perceiving hidden messages and thinking you're linked with a conspiracy. Everything seems to be tied with logic into a cohesive whole, no weird memory gaps or alternate personalities.
There are different forms of schizophrenia, such as paranoid schizophrenia, catatonic schizophrenia and hebephrenic schizophrenia, in which some or most of the symptoms associated with schizophrenia are not present.
Paranoid schizophrenia is most well-known, and is associated with delusions (such as GP comment outlined).
Schizophrenia in general is associated with severe anxiety and depression, explaining your friends' experiences.
Note that I'm not even close to the remotest possible thing to a doctor, and have no special insight - most of my 'knowledge' about schizophrenia should be treated with caution at best.
I know 3-4 people with schizophrenia, and none of them displayed the kind of wild delusions you're describing (though I am not discounting them! Don't get me wrong). In my experience schizophrenia manifests itself more like a worse form of anxiety, paranoia and depression mixed together (all my friends are under treatment and medicated).