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.