Schizophrenia’s diagnosis require the usage of several tests and observation techniques to understand the type of schizophrenia, an individual might be suffering from. A psychiatrist is required to observe several symptoms that fall under the criteria of ICD (International Classification of diseases) and DSM (Diagnostic and Statistical Manual of Mental Disorders). Under this criteria, a person can be diagnosed with schizophrenia on the basis of presence of at least three symptoms like delusions (false beliefs held on inadequate grounds), hallucinations and disorganized speech. Patients may also be diagnosed on the basis of catatonic behavior (assuming awkward positions for hours).

The major tool for defining schizophrenia is observation. The psychiatrist may note if the above symptoms are causing social or occupational distress for a significant duration (one month of symptoms). Observation can help a professional to understand if the person is suffering from schizophrenia or other related psychotic disorders such as schizo-affective disorder or mood disorder.

CT Scan or Computed Tomography can help in understanding the underlying cause for the behavior associated with Schizophrenia symptoms. A CT Scan can rule out the possibilities of brain injury or other related problems that might cause hallucinations or delusions. The psychiatrist will also rule out different illnesses such as HIV or epilepsy or brain lesions. 

Blood tests help to determine whether the behavior symptoms exhibited by the client can be attributed to substance abuse. Generally, people who take illegal drugs such as cocaine or hash may also exhibit symptoms of hallucinations, delusions and formal thought disorders. But schizophrenia can only be diagnosed if it does not involve the effects of drugs or alcohol.

If the symptoms of schizophrenia overlap the symptoms of other psychological disorders such as depression or bipolar disorder then the psychiatrist may perform a detailed medical and neurological examination. The psychiatrist in some cases may also make a dual diagnosis based on the neurological examination. For instance, a dual diagnosis would include presence of psychotic symptoms along with borderline personality disorder or bipolar disorder.

Some universities have designed special IQ tests that can trace the presence of psychotic symptoms and schizophrenia. Although, the tests are still in their infancy, yet in long run they can provide detailed analysis and diagnosis of this disorder.

For patients who may exhibit tactile or olfactory hallucinations (something crawling in stomach or smell of poison or smoke), smell tests can be used to diagnose schizophrenia.

These tests use a variety of less structured or unstructured stimuli and allow the individual to project her/his feelings and desires. These tests assess unconscious motives and feelings, providing insight about whether a person may be suffering from schizophrenia or can develop the disorder. Tests like ‘Thematic Apperception Test’, ‘Rorschach ink blot tests’ can be used for this purpose.

Interviewing the patient can help a psychiatrist recognize the type and kind of schizophrenia that a person may be suffering from. This will allow a detailed analysis and personalized treatment. According to DSM (Diagnostic Statistical Manual of Mental Disorders), schizophrenia is of five types – paranoid type in which a person is preoccupied with delusions and auditory hallucinations, disorganized type wherein the person has a disorganized speech and behavior, catatonia type wherein the person has an extreme motor immobility or inactivity, undifferentiated type wherein the individual doesn’t fit a type but has the symptoms and residual type, wherein the individual has negative symptoms.