Delusional disorder might make you think you're something you're not. Schizophrenia might make it so more than one voice inside your head tries to convince you of same.

There are many delusional disorders, such as personality disorder. There are different "checklists" for each type of disorder, so it is best to see a doctor or therapist (or better yet, combine both to get a psychiatrist). Many disorders produce delusions, and it often has to do with dopamine production in the brain. It is particularly difficult to distinguish between schizophrenia and schizophreniform disorder. There is a connection between bipolar or mood disorders and schizophrenia, and they can sometimes be confused. You should check the DSM or ICD for diagnosis criterion of any disorder invonving delusions. You can find the ICD at: http://en.wikipedia.org/wiki/ICD My final answer: Have a distinguished psychiatrist diagnose a disorder. A short story: A friend of mine with various problems was diagnosed with schizophrenia, but she was only bulimic. She was prescribed Zyprexa (hope the spelling is correct), and it helped with many symptoms because the drug helps with both. But she did not conquer her problems yet. It took a second doctor to treat her problems individually before she got the proper meds and diagnosis. In short, see a doctor (or two) for a correct diagnosis. Some disorders can look alike, and a professional is trained to distinguish between them.

Refer to the DSM-IV and you will quickly see the critera listed...I believe another user gave a link to a site that will allow you to do just that. Sorry I only have my hard copy of the DSM and am not familiar with a web listing.

Delusional disorder is characterized by a the delusion being unaccommpanied by any hallucination and is usually logically and internally consistent. That is, it makes complete sense if thought though - it's the premise upon which it's built that's questionable - in fact so questionable, it's delusional. The delusion is often life-long and may be thematically one of eroticism, jealousy, grandiosity, persecution, or somatic in nature (e.g creepy-crawlies all over me). The sufferers general social functioning is often unaffected in any negative way. In contrast, schizophrenia is characterized by delusions and/or hallucinations and although these may indeed be highly systematized (internally consistent or logical), they have many holes that have gone unaddressed by the sufferer - the logic is faulty and their thoughts are very often disorganized or badly connected. The sufferer may recover fully (about 33%) or have repeated events (33%) or continuous illness. They are often dysfunctional and suffer 'negative symptoms' - depression, anxiety, flat affect. It's these symptoms which more often than not, appear first.