Diagnosis of schizophrenia
The diagnosis of schizophrenia is based on criteria in either the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, version DSM-IV-TR, or the World Health Organization's International Statistical Classification of Diseases and Related Health Problems, the ICD-10. These criteria use the self-reported experiences of the person and reported abnormalities in behavior, followed by a clinical assessment by a mental health professional. Symptoms associated with schizophrenia occur along a continuum in the population and must reach a certain severity before a diagnosis is made.
The ICD-10 criteria are typically used in European countries, while the DSM-IV-TR criteria are used in the United States and the rest of the world, and are prevailing in research studies. The ICD-10 criteria put more emphasis on Schneiderian first-rank symptoms. In practice, agreement between the two systems is high.
According to the revised fourth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-IV-TR), to be diagnosed with schizophrenia, three diagnostic criteria must be met:
- Characteristic symptoms: Two or more of the following, each present for much of the time during a one-month period (or less, if symptoms remitted with treatment).
- Disorganized speech, which is a manifestation of formal thought disorder
- Grossly disorganized behavior (e.g. dressing inappropriately, crying frequently) or catatonic behavior
- Negative symptoms: Blunted affect (lack or decline in emotional response), alogia (lack or decline in speech), or avolition (lack or decline in motivation)
- If the delusions are judged to be bizarre, or hallucinations consist of hearing one voice participating in a running commentary of the patient's actions or of hearing two or more voices conversing with each other, only that symptom is required above. The speech disorganization criterion is only met if it is severe enough to substantially impair communication.
- Social or 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.
- Significant duration: Continuous signs of the disturbance persist for at least six months. This six-month period must include at least one month of symptoms (or less, if symptoms remitted with treatment).
If signs of disturbance are present for more than a month but less than six months, the diagnosis of schizophreniform disorder is applied. Psychotic symptoms lasting less than a month may be diagnosed as brief psychotic disorder, and various conditions may be classed as psychotic disorder not otherwise specified. Schizophrenia cannot be diagnosed if symptoms of mood disorder are substantially present (although schizoaffective disorder could be diagnosed), or if symptoms of pervasive developmental disorder are present unless prominent delusions or hallucinations are also present, or if the symptoms are the direct physiological result of a general medical condition or a substance, such as abuse of a drug or medication.
- Paranoid type: Where delusions and hallucinations are present but thought disorder, disorganized behavior, and affective flattening are absent. (DSM code 295.3/ICD code F20.0)
- Disorganized type: Named hebephrenic schizophrenia in the ICD. Where thought disorder and flat affect are present together. (DSM code 295.1/ICD code F20.1)
- Catatonic type: The subject may be almost immobile or exhibit agitated, purposeless movement. Symptoms can include catatonic stupor and waxy flexibility. (DSM code 295.2/ICD code F20.2)
- Undifferentiated type: Psychotic symptoms are present but the criteria for paranoid, disorganized, or catatonic types have not been met. (DSM code 295.9/ICD code F20.3)
- Residual type: Where positive symptoms are present at a low intensity only. (DSM code 295.6/ICD code F20.5)
- Post-schizophrenic depression: A depressive episode arising in the aftermath of a schizophrenic illness where some low-level schizophrenic symptoms may still be present. (ICD code F20.4)
- Simple schizophrenia: Insidious and progressive development of prominent negative symptoms with no history of psychotic episodes. (ICD code F20.6)
Psychotic symptoms may be present in several other mental disorders, including bipolar disorder, borderline personality disorder, drug intoxication and drug-induced psychosis. Delusions ("non-bizarre") are also present in delusional disorder, and social withdrawal in social anxiety disorder, avoidant personality disorder and schizotypal personality disorder. Schizophrenia is complicated with obsessive-compulsive disorder (OCD) considerably more often than could be explained by pure chance, although it can be difficult to distinguish obsessions that occur in OCD from the delusions of schizophrenia.
A more general medical and neurological examination may be needed to rule out medical illnesses which may rarely produce psychotic schizophrenia-like symptoms, such as metabolic disturbance, systemic infection, syphilis, HIV infection, epilepsy, and brain lesions. It may be necessary to rule out a delirium, which can be distinguished by visual hallucinations, acute onset and fluctuating level of consciousness, and indicates an underlying medical illness. Investigations are not generally repeated for relapse unless there is a specific medical indication or possible adverse effects from antipsychotic medication.
Early, late, and very late onset
Early-onset schizophrenia refers to individuals who had their first episode of symptoms at age 20-30. Late-onset refers to those whose first episode of symptoms began after the age of 40. Very-late-onset refers to those with their first episode of symptoms at age 60 and older. It is estimated that 15% of the population with schizophrenia are late-onset and 5% are very-late onset.
Many of the symptoms of late-onset schizophrenia are similar to the early-onset. However, individuals with late-onsets are more likely to report:
- Visual, tactile, and olfactory hallucinations
- Persecutory delusion
- Partition delusions
- Third-person, running commentary
- Accusatory or abusive auditory hallucinations
- Formal thought disorder
- Affective flattening or blunting
- Less formal thought disorder or cognitive impairment
- Fewer negative symptoms
There is an argument that the underlying issues would be better addressed as a spectrum of conditions or as individual dimensions along which everyone varies rather than by a diagnostic category based on an arbitrary cut-off between normal and ill. This approach appears consistent with research on schizotypy, and with a relatively high prevalence of psychotic experiences, mostly non-distressing delusional beliefs, among the general public. In concordance with this observation, psychologist Edgar Jones, and psychiatrists Tony David and Nassir Ghaemi, surveying the existing literature on delusions, pointed out that the consistency and completeness of the definition of delusion have been found wanting by many; delusions are neither necessarily fixed nor false, and need not involve the presence of incontrovertible evidence.
Nancy Andreasen has criticized the current DSM-IV and ICD-10 criteria for sacrificing diagnostic validity for the sake of artificially improving reliability. She argues that overemphasis on psychosis in the diagnostic criteria, while improving diagnostic reliability, ignores more fundamental cognitive impairments that are harder to assess due to large variations in presentation. This view is supported by other psychiatrists. In the same vein, Ming Tsuang and colleagues argue that psychotic symptoms may be a common end-state in a variety of disorders, including schizophrenia, rather than a reflection of the specific etiology of schizophrenia, and warn that there is little basis for regarding DSM’s operational definition as the "true" construct of schizophrenia. Neuropsychologist Michael Foster Green went further in suggesting the presence of specific neurocognitive deficits may be used to construct phenotypes that are alternatives to those that are purely symptom-based. These deficits take the form of a reduction or impairment in basic psychological functions such as memory, attention, executive function and problem solving.
The exclusion of affective components from the criteria for schizophrenia, despite their ubiquity in clinical settings, has also caused contention. This exclusion in the DSM has resulted in a "rather convoluted" separate disorder—schizoaffective disorder. Citing poor interrater reliability, some psychiatrists have totally contested the concept of schizoaffective disorder as a separate entity. The categorical distinction between mood disorders and schizophrenia, known as the Kraepelinian dichotomy, has also been challenged by data from genetic epidemiology.
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