It is known that no single symptom is specific to schizophrenia, so, in order to put a diagnosis, there must be some conditions present. We can mention 3 conditions. A condition is about certain symptoms that are present for at least six months even in the absence of active flare-ups, and include symptoms like marked social withdrawal, peculiar behavior, vague and incoherent speech, and other symptoms of disturbed thinking. The second condition is about the presence of at least one active flare-up lasting a month or less, consisting of at least two characteristic symptoms, like hallucinations, delusions, disorganized thinking and other. The third condition is about particularly bizarre delusions or hallucinations that appear in patients even in the absence of other characteristic symptoms.

Symptoms that occur in schizophrenia can also appear in other psychological and medical conditions. These symptoms include delusions, hallucinations, disorganized and incoherent speech, and bizarrely disorganized or catatonic behavior.There are some conditions that resemble schizophrenia. Depression can sometimes occur together with somatic delusions which means that depression comes with delusions that focus on a physical abnormality or disease that isn't real.People with bipolar disorder can experience during the manic phase paranoia and delusions of grandeur. There are also the schizophrenia-like psychoses, conditions that may be variations of entirely different diseases, and are classified as schizoaffective disorder, schizophreniform psychosis, and atypical and brief reactive schizophrenia.Alcohol and drug abuse can also trigger psychosis, and it is important that doctors distinguish psychosis triggered by drugs or alcohol from a schizophrenic episode.Encephalitis, neurosyphilis, thyroid disorders, cancr in the central nervous system, Huntington's disease, multiple sclerosis, stroke, Wilson's disease and other diseases can also be causes of psychotic symptoms.It was seen that some medications, because of the side effects they bring may induce psychosis, and this is usually observed in elderly patients.

In detecting changes in the brain structure that relate to specific sets of symptoms in schizophrenia, there are a number of brain imaging techniques, but at this time, they are used only as research tools.Magnetic resonance imaging can show the brain from a number of different perspectives, and it reveals parts of the brain that are inaccessible to other scanning methods.Other imaging techniques are single photon emission computed tomography and positron emission tomography. They can show information on blood flow and metabolism in the brain.Science is about to develop some simple tests, that can detect schizophrenia accurately and early enough to initiate preventive measures. There can be useful a blood test that detects genetic evidence of high levels of D3 dopamine receptor, measurements of certain esters, and a test that uses computers to analyze brain scans and identify changes in blood flow indicative of schizophrenia, even before symptoms occur.