When mental health professionals give a diagnosis of schizophrenia, they base their decision on the criteria that is delineated by either the American Psychiatric Association in their definitive text, the Diagnostic and Statistical Manual of Mental Disorders, or by the World Health Organization’s text, the International Statistical Classification of Diseases and Related Health Problems. The current version’s are the DSM-IV-TR and the ICD-10.
The way that it functions is two-fold. The person experiencing schizophrenic symptoms must report their own feelings, thoughts, and emotions. Others, including friends, family, and the psychiatrist or psychologist themselves will observe strangeness in behavior and take note of the abnormalities. Then, a trained professional must perform a full clinical assessment in order to make the subjective decision of whether or not the diagnosis is appropriate or not.
While the ICD-10 is used in Europe, the DSM-IV-TR is being used everywhere else in the world, including the U.S., so we will follow that set of criteria. They are similar enough that it makes little difference.
The Diagnostic Criteria
When following the DSM-IV-TR, there are three specific criteria that must be present, with certain time parameters attached, before a diagnosis of schizophrenia will be given. These are (and I paraphrase):
- Characteristic Symptoms: At least two of the following list of symptoms must be manifest for a majority of a period of at least six months:
- Disorganized speech (indicative of a thought disorder)
- Extreme positive or negative behaviors (such as overly emotional or catatonic postures)
- Negatives symptoms (such as a flattened affect, alogia, or avoliton, all being a lack of response)
- Note – If the delusions of the patient are deemed by the professional to be very bizarre, then only that one symptom is required. If the hallucinations feature one or more voices conversing and keeping a running commentary of dialogue, then only that one symptom is required. Speech disorganization must significantly impair communication to count.
- Dysfunction in Social Life or Occupation: Since the onset of symptoms, at least one major area of life, including hygiene, work, or socializing, have been significantly impaired.
- Significant Duration: The disturbances associated directly with the symptoms must have persisted for at least six months, with one month of acute symptoms being present.
There are times when schizophrenic symptoms are present longer than a month’s time but subsist before the six-month mark. In this case, a diagnosis of a schizophreniform disorder is possible. If symptoms persist for less than thirty days, a diagnosis of a brief psychotic disorder is a possibility.
Schizophrenia will not be diagnosed if the symptoms are minimal relative to others that can be related to a mood disorder. In this case, there is the possibility of a schizoaffective disorder diagnosis. If the symptoms can be attributed to a specific medical condition or use of a medication or illicit substance, then a diagnosis of schizophrenia will not be made.
The Diagnosis of Schizophrenia Subtypes
Currently there are five subtypes of schizophrenia in the DSM-IV-TR, and the ICD-10 adds another two sub-classifications. These are:
- Post-Schizophrenic Depression (ICD-10 only)
- Simple Schizophrenia (ICD-10 only)
These are fairly simple to understand once you understand the characteristics associated with each one. Undifferentiated schizophrenia has an exhibition of psychosis without specific criteria for other subtypes having been met. The paranoid subtype features hallucinations and delusions with an absence of disorganization of thought and behavior. The catatonic subtype features an absence of movement, an immobilization of meaningful and purpose-driven movement. It may also feature repetitive and purposeless behaviors. The disorganized subtype is used when a blunted affect is comorbid with thought disorder. The residual subtype is simply when features have become low in intensity but still present.
The ICD-10 only sub-classifications are described as follows. The post-schizophrenic depression is a time of depression after the time of the most acute symptoms, in which a low-level intensity of symptoms are still manifest, yet the depression is the prominent feature. The simple schizophrenia subtype is the prominence of negative symptoms with no symptoms of the positive kind having been a part of this person’s biographical history.
Peculiarities in Diagnosis
There are some peculiarities when it comes to diagnosing schizophrenia. Nothing is cut and dry in the medical sciences, especially with very complex illnesses. The first peculiarity to consider is that of the dual diagnosis.
Dual Diagnosis with Schizophrenia
Many of the symptoms that are important for a schizophrenia diagnosis are large indicators of other mental illnesses as well. For instance, the psychotic symptoms such as delusions and hallucinations are a part of drug-induced psychosis and bipolar disorder, and more. The social isolation that can occur with schizophrenia is a major indicator of social anxiety disorder and personality disorders such as avoidant and schizotypal. Obsessive-compulsive disorder is often comorbid with schizophrenia more times than chance would dictate, meaning there is some relation or confusion between the two. There are also medical conditions that can produce symptoms that closely resemble those of schizophrenia, such as syphilis, epilepsy, delirium, metabolic problems, and brain lesions.
The Time of Onset of Symptoms
Schizophrenia manifests itself at different times in people’s lives. Depending on this time frame, there will be a specific label associated, such as early, late, or very late onset. Early onset of schizophrenia occurs when the initial schizophrenic episode occurs between the second and third decades of a person’s life. Late onset begins from the age of 40 up to 64 years of age. Very late onset schizophrenia begins at the age of 65 or beyond. Studies indicate that around 80% of schizophrenics experienced an early onset, while 15% experienced a late onset. The last 5% are very late onset.
Late onset schizophrenics are more likely to experience hallucinations and delusions, especially of the paranoia-kind, such as persecution beliefs and abusive voices. They are less likely to have a disorganization of thought or a blunted affect. Very late onset schizophrenics are less likely to have cognitive disorders and negative symptoms.
The above are the specific schizophrenia diagnostic criteria as set in place by the DSM-IV-TR. This is exactly what is used by medical professional all over the world, except for in European countries where they follow the ICD-10, which is very close and in high agreement with the DSM-IV-TR. If you have recently been diagnosed or know someone who has been, you can now read and know exactly what criteria you or they met to achieve the diagnosis.