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How does a doctor know someone has schizophrenia?

There are no blood tests or x-rays that can tell a doctor if a person has schizophrenia. Doctors rely on what a person and their family tells them about what has been going on to decide if a person has schizophrenia. Doctors and mental health workers use a book to determine what mental illness a person may have. The book is called the Diagnostic and Statistical Manual of Mental Disorders (DSM). It describes the symptoms of different mental illnesses, and how long a person must have each symptom.

What does the DSM say about schizophrenia?

The DSM says that a person has schizophrenia if they have two of the following symptoms for much of the time during a 1month period. Also, remember not everyone has all of these symptoms. And not everyone has exactly the same symptoms.

bulletHaving strange ideas or thinking someone is out to get them.
bulletHearing voices talking about them or to them. The voices usually say mean things.
bulletSpeech that does not make sense or they make up words. A person might not be able to talk very well. They might have a hard time carrying on a conversation.
bulletDoing strange things that they would not normally do.
bulletNot moving or motionless behavior, someone looks “frozen” (catatonic).
bulletNo facial expressions, blank stares, lack of energy. These are sometimes called negative symptoms.
bulletHaving problems at work, trouble being with others, or not wanting to take care of themselves. For example, a person with schizophrenia might start a project and not finish it. They might have trouble finishing anything. Or they cannot make up their mind about what to do. Sometimes, when someone is really sick, they cannot take care of themselves. They may have to be told to take a bath or to eat something.

There are five types of schizophrenia

There are five different types of schizophrenia. Since people with schizophrenia do not show all of the exact same signs, the DSM lists five different types of schizophrenia.

1. Paranoid

With this type of schizophrenia, a person often hears voices and believes many things that are not true. These are called delusions.

2. Catatonic

With this type of schizophrenia, a person will sometimes sit in an odd position for a long time. They might look like they are “frozen”.

3. Disorganized

With this type of schizophrenia, a person might make up words and make no sense when speaking. Often times, their thoughts do not make sense. A person with this type might say the same things over and over again like a broken record.

4. Residual type

With this type of schizophrenia, a person has some symptoms but not that bad, and not as many. It is like having schizophrenia, but at a lesser level.

5. Undifferentiated type

With this type of schizophrenia, a person might have the symptoms of the illness, but do not quite fit into any other type.

Read on for more about what the DSM says about schizophrenia

The Diagnostic Criteria (DSM) is the book mental health workers and doctors look at to find out if someone has schizophrenia.  There are several versions of the DSM.  They change it a bit every few years because of new developments in science.  The latest version is called the DSM-IV-TR.  Listed below is what you would find written in the DSM about schizophrenia.  Some of it can be hard to read and understand. 

Characteristic symptoms

Two (or more) of the following, each present for a significant portion of time during a 1-month period (or less if successfully treated):

1. Delusions

2. Hallucinations

3.Disorganized speech (e.g., frequent derailment or incoherence)

4.Grossly disorganized or catatonic behavior

5. Negative symptoms affective flattening, alogia, or avolition)

Note: Only one Criterion A symptom is required if delusions are bizarre or hallucinations consist of a voice keeping up a running commentary on the person's behavior or thoughts, or two or more voices conversing with each other.

bulletDuring the same period of illness, there have been delusions or hallucinations for at least 2 weeks in the absence of prominent mood symptoms.
bulletSymptoms that meet criteria for a mood episode are present for a substantial portion of the total duration of the active and residual periods of the illness.
bulletThe disturbance is not due to the direct physiological effects of a substance (e.g. drug of abuse, a medication) or a general medical condition.

Social/occupational dysfunction

For a significant portion of the time since the onset of the disturbance, one or more major areas of functioning such as work, interpersonal relations, or self-care are markedly below the level achieved prior to the onset (or when the onset is in childhood or adolescence, failure to achieve expected level of interpersonal, academic, or occupational achievement).


Continuous signs of the disturbance persist for at least 6 months.  This 6-month period must include at least 1 month of symptoms (or less if successfully treated) that meet Criterion A (i.e., active-phase symptoms) and may include periods of prodromal or residual symptoms.  During these prodromal or residual periods, the signs of the disturbance may be manifested by only negative symptoms or two or more symptoms listed in Criterion A present in an attenuated form (e.g., odd beliefs, unusual perceptual experiences).

Schizoaffective and Mood Disorder Exclusion

Schizoaffective Disorder and Mood Disorder With Psychotic Features have been ruled out because either (1) no Major Depressive Episode, Manic Episode, or Mixed Episode have occurred concurrently with the active-phase symptoms; or (2) if mood episodes have occurred during active-phase symptoms, their total duration has been brief relative to the duration of the active and residual periods.

Substance/general medical condition exclusion

The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition.

Relationship to a pervasive developmental disorder

If there is a history of Autistic Disorder or another Pervasive Developmental Disorder, the additional diagnosis of Schizophrenia is made only if prominent delusions or hallucinations are also present for at least a month (or less if successfully treated).