Schizophrenia is diagnosed on the basis of symptom profiles. Neural correlates do not provide sufficiently useful criteria. Diagnosis is based on the self-reported experiences of the person, and abnormalities in behavior reported by family members, friends or co-workers, followed by a clinical assessment by a psychiatrist, social worker, clinical psychologist or other mental health professional. Psychiatric assessment includes a psychiatric history and some form of mental status examination.
The most widely used standardized criteria for diagnosing schizophrenia come from the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, version DSM-IV-TR, and the World Health Organization's International Statistical Classification of Diseases and Related Health Problems, the ICD-10. The latter criteria are typically used in European countries, while the DSM criteria are used in the United States and the rest of the world, as well as prevailing in research studies. The ICD-10 criteria put more emphasis on Schneiderian first-rank symptoms, although, 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 - affective flattening (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/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.
- 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).
Schizophrenia cannot be diagnosed if symptoms of mood disorder or pervasive developmental disorder are present, or the symptoms are the direct result of a general medical condition or a substance, such as abuse of a drug or medication.
Confusion with other conditions
Psychotic symptoms may be present with several other psychiatric illnesses, including bipolar disorder, borderline personality disorder, schizoaffective disorder, drug intoxication, either intoxicated or abstinent drug-induced psychosis, and schizophreniform 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 compulsions that represent OCD from the delusions characteristic of the 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.
"Schizophrenia" does not mean dual personality, despite the etymology of the word (Greek σχίζω = "I split").
The DSM-IV-TR contains five sub-classifications of schizophrenia.
- 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)
The ICD-10 defines two additional subtypes.
- 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)
Controversies and Research Directions
Part of a larger controversy over biopsychiatry, the validity of schizophrenia as a diagnostic entity has been criticised by number of psychologists as lacking in scientific validity and diagnostic reliability. In 2006, a group of patients and mental health professionals from the UK, under the banner of Campaign for Abolition of the Schizophrenia Label, argued for a rejection of the diagnosis of schizophrenia based on its heterogeneity and associated stigma, and called for the adoption of a bio-psychosocial model. Other UK psychiatrists opposed the move arguing that the term schizophrenia is a useful, even if provisional concept.
The discrete category of schizophrenia used in the DSM has also been criticized. As with other psychiatric disorders, some psychiatrists have suggested that the diagnosis would be better addressed as individual dimensions along which everyone varies, such that there is a spectrum or continuum rather than a 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, nor involve the presence of incontrovertible evidence.
Nancy Andreasen, a leading figure in schizophrenia research, has criticized the current DSM-IV and ICD-10 criteria for sacrificing validity for the sake of improving diagnostic 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 become a bone of 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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