The diagnosis of schizophrenia, a psychotic disorder, is based on criteria in either the American Psychiatric Association's Diagnostic and Statistical Manual of Mental Disorders, or the World Health Organization's International Classification of Diseases (ICD). Clinical assessment of schizophrenia is carried out by a mental health professional based on observed behavior, reported experiences, and reports of others familiar with the person. Diagnosis is usually made by a psychiatrist. Associated symptoms occur along a continuum in the population and must reach a certain severity and level of impairment before a diagnosis is made. Schizophrenia has a prevalence rate of 0.3-0.7% in the United States.
Criteria In 2013, the American Psychiatric Association released the fifth edition of the DSM (DSM-5). According to the manual, to be diagnosed with schizophrenia, two diagnostic criteria have to be met over much of the time of a period of at least one month, with a significant impact on social or occupational functioning for at least six months. The DSM diagnostic criteria outlines that the person has to be experiencing either delusions, hallucinations, or disorganized speech. In other words, an individual does not have to be experiencing delusions or hallucinations to receive a diagnosis of schizophrenia. A second symptom could be negative symptoms, or severely disorganized or catatonic behavior. Only two symptoms are required for a diagnosis of schizophrenia, resulting in different presentations for the same disorder.
In practice, agreement between the two systems is high. The DSM-5 criteria puts more emphasis on social or occupational dysfunction than the ICD-10. The ICD-10, on the other hand, puts more emphasis on first-rank symptoms. The current proposal for the ICD-11 criteria for schizophrenia recommends adding self-disorder as a symptom.
Changes made Both manuals have adopted the chapter heading of Schizophrenia spectrum and other psychotic disorders; ICD modifying this as Schizophrenia spectrum and other primary psychotic disorders. The definition of schizophrenia remains essentially the same as that specified by the 2000 text revised DSM-IV (DSM-IV-TR). However, with the publication of DSM-5, the APA removed all sub-classifications of schizophrenia. ICD-11 has also removed subtypes. The removed subtype from both, of catatonic has been relisted in ICD-11 as a psychomotor disturbance that may be present in schizophrenia.
Another major change was to remove the importance previously given to Schneider's first-rank symptoms. DSM-5 still uses the listing of schizophreniform disorder but ICD-11 no longer includes it. DSM-5 also recommends that a better distinction be made between a current condition of schizophrenia and its historical progress, to achieve a clearer overall characterization.
A dimensional assessment has been included in DSM-5 covering eight dimensions of symptoms to be rated (using the Scale to Assess the Severity of Symptom Dimensions) – these include the five diagnostic criteria plus cognitive impairments, mania, and depression. This can add relevant information for the individual in regard to treatment, prognosis, and functional outcome; it also enables the response to treatment to be more accurately described.
Two of the negative symptoms – avolition and diminished emotional expression – have been given more prominence in both manuals.
First rank symptoms First-rank symptoms are psychotic symptoms that are particularly characteristic of schizophrenia, which were put forward by Kurt Schneider in 1959.Schneider, K. Clinical Psychopathology. New York: Grune and Stratton. 1959. Their reliability for the diagnosis of schizophrenia has been questioned since then. A 2015 systematic review investigated the diagnostic accuracy of first rank symptoms: + First rank symptoms for schizophrenia Summary These studies were of limited quality. Results show correct identification of people with schizophrenia in about 75–95% of the cases although it is recommended to consult an additional specialist. The sensitivity of FRS was about 60%, so it can help diagnosis and, when applied with care, mistakes can be avoided. In lower resource settings, when more sophisticated methods are not available, first rank symptoms can be very valuable. Summary accuracy % (95% CI) Prevalence median (range) Implications Quality and comments Diagnosis of schizophrenia from all other diagnoses Sensitivity 57.0 (50.4, 63.3) Specificity 81.4 (74.0, 87.1) 48% (15% to 84%) Prevalence of 48%: 48 out of every 100 people with all other mental health diagnoses will have schizophrenia. The result means that, of these, 21 will not be identified as having schizophrenia by use of FRS (43% of 48). Then, of the 52 people really without schizophrenia, 10 may be incorrectly diagnosed with schizophrenia by the FRS. Diagnosis of schizophrenia from other types of psychosis Sensitivity 58.0 (50.3, 65.3) Specificity 74.7 (85.2, 82.3) 57% (24% to 84%) Prevalence of 57%: 57 out of every 100 people with other types of psychosis will have schizophrenia. The result means that, of these, 24 will not be identified as having schizophrenia by use of FRS (42% of 57). Then, of the 43 people really without schizophrenia, 13 may be incorrectly diagnosed with schizophrenia by the FRS. For all three estimates there are important issues regarding patient selection, use of index test and reference standard. This raises doubts about the accuracy of these findings. Also most studies were not conducted in an everyday clinical setting. Diagnosis of schizophrenia from non-psychotic disorders Sensitivity 61.8 (51.7, 71.0) Specificity 94.1 (88.0, 97.2) 55% (19% to 89%) With a prevalence of 55%, 55 out of every 100 people with non-psychotic disorders will have schizophrenia. Of these, 21 will not be identified as having schizophrenia by use of FRS (38% of 55). Then, of the 45 people really without schizophrenia, 3 may be incorrectly diagnosed with schizophrenia by the FRS.
Heterogeneity
Sub-classifications The DSM-IV-TR contained five sub-classifications of schizophrenia. The sub-classifications were removed in the DSM-5 due to the conditions' heterogeneous nature and their historical insignificance in clinical practice. These were retained in previous revisions largely for reasons of tradition, but had subsequently proved to be of little worth.
The ICD-10 defines seven sub-classifications of schizophrenia. These sub-classifications are:
+ Sub-classifications of Schizophrenia ICD-10 Description DSM-IV-TR EquivalentParanoid (F20.0)Delusions and hallucinations are present but thought disorder, disorganized behavior, and affective flattening are not prominent.Paranoid type (295.3)Hebephrenic (F20.1)Thought disorder and flat affect are present together.Disorganized type (295.1)Catatonic (F20.2)Psychomotor disturbances are dominant features. Symptoms can include catatonic stupor and waxy flexibility.Catatonic type (295.2)Undifferentiated (F20.3)Psychotic symptoms are present but the criteria for paranoid, disorganized, or catatonic types have not been met.Undifferentiated type (295.9)Post-schizophrenic depression (F20.4)A depressive episode arising in the aftermath of a schizophrenic illness where some low-level schizophrenic symptoms may still be present.Not presentResidual (F20.5)Positive symptoms are present at a low intensity and negative symptoms are prominent.Residual type (295.6)Simple (F20.6)Delusions and hallucinations are not evident and negative symptoms progress slowly.Not presentOther (F20.8)Includes cenesthopathic schizophrenia and schizophreniform disorder NOS Not present
Country-specific versions The ICD-10 Clinical Modification, used for medical coding and reporting in the United States excludes the post-schizophrenic depression (F20.4) and the Simple (F20.6) sub-classifications.
The Russian version of the ICD-10 includes additional four sub-classifications of schizophrenia: hypochondriacal (F20.801), cenesthopathic (F20.802), childhood type (F20.803), and atypical (F20.804).
Comorbidities People with schizophrenia often have additional mental health problems such as anxiety, depressive, or substance-use disorders. Schizophrenia occurs along with obsessive-compulsive disorder (OCD) considerably more often than could be explained by chance. An estimated 21% to 47% of patients with schizophrenia have a substance misuse disorder at some time in their life, and the chances of developing a substance misuse disorder is significantly higher among patients with a psychotic illness. All of these factors result in an increased range of clinical presentations and suggest a significant etiological heterogeneity.
Sex differences Schizophrenia is diagnosed 1.4 times more frequently in males than females, with onset peaking at ages 20–28 years for males and 4–10 years later in females. Females show more psychotic and affective symptoms than males, and have less social impairment. Men present more often with negative symptoms and disorganization. These differences are likely due to the protective effects of estrogen and are correlated with estrogen expression.
Prelingually deaf persons Usually, psychiatric diagnostics is carried out orally. Thus, the question about schizophrenia in prelingually deaf persons rises. Only few reports exist. A review points out that acoustic hallucinations of normal hearing schizophrenic people correspond to visual and tactile hallucinations of prelingually deaf persons. Also, the structure of the (sign-) language is altered in ill persons. As a follow, "schizophrenia does not depend on the acoustic part of language or the acquisition of spoken language".
Onset Early-onset schizophrenia occurs before the age of 17, and very-early onset schizophrenia occurs before the age of 13. late-onset occurs after the age of 40, and very-late-onset after the age of 60. It is estimated that 15% of the population with schizophrenia are late-onset and 5% 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 hallucinations in all sensory modalities, as well as persecutory and partition delusions. On the other hand, late-onset cases are less likely to present with formal thought disorder, affective symptoms. Negative symptoms and cognitive impairment are also rarer in very-late onset cases.
Etiology The pathophysiology of schizophrenia is poorly understood. Multiple hypotheses have been put forward, with evidence both supporting and contradicting them. The most commonly supported theories are the dopamine hypothesis and the glutamate hypothesis. Multiple genetic and environment factors have been associated with increased risk for developing schizophrenia. Furthermore, response to treatment with anti-psychotic medication is variable, with some patients being resistant to some therapies.Semple.David"Oxford Handbook Of Psychiatry". Oxford Press. 2005. p 207. Together, the differences in causes, response to treatment and pathophysiology suggest schizophrenia is heterogeneous from an etiological standpoint. The differences resulting from this in terms of in clinical manifestations make the disorder harder to diagnose.
Genetic Multiple genetic and environmental factors contribute to the development of the schizophrenic phenotype. Distinct symptomatic sub types of schizophrenia groups show distinct patterns of SNP variations, reflecting the heterogeneous nature of the disease. Studies also suggest there is a genetic overlap between schizophrenia and other psychiatric disorders, such as autism spectrum disorders, attention deficit-hyperactivity disorder, bipolar disorder, and major depressive disorder. These factors complicate the use of genetic tests in diagnosis or prediction of the onset of schizophrenia.
Differential diagnosis