One of the most common symptom of schizophrenia is paranoia. People who suffer from schizophrenia are under the delusion that somebody or something is out to get them.
Another common symptom among those that suffer from schizophrenia is hallucinations.
They hear voices or see people or things that are not there.
Lack of care for personal hygiene especially from someone who is otherwise very well kept and clean.
A person that is normally an outgoing person for no apparent reason becoming withdrawal or going into a social isolation.
Displaying a manic-depressive behaviour which is a disorder in itself but often accompanies those who suffer from schizophrenia. That is at times showing the lack of emotions, showing great outbursts of anger, and generally emotions not matching the situation.
Having trouble concentrating on school and work.