Diagnosis of schizophrenia

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.^[5] Only two symptoms are required for a diagnosis of schizophrenia, resulting in different presentations for the same disorder.^[5]

In practice, agreement between the two systems is high.^[6] The DSM-5 criteria puts more emphasis on social or occupational dysfunction than the ICD-10.^[7] The ICD-10, on the other hand, puts more emphasis on first-rank symptoms.^[2][8] The current proposal for the ICD-11 criteria for schizophrenia recommends adding self-disorder as a symptom.^[9]

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.^[10] 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.^[10] 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.^[10]

Another major change was to remove the importance previously given to Schneider's first-rank symptoms.^[11] DSM-5 still uses the listing of schizophreniform disorder but ICD-11 no longer includes it.^[10] 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.^[11]

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.^[10] 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.^[10][12]

Two of the negative symptoms – avolition and diminished emotional expression – have been given more prominence in both manuals.^[10]

First-rank symptoms are psychotic symptoms that are particularly characteristic of schizophrenia, which were put forward by Kurt Schneider in 1959.^[13] Their reliability for the diagnosis of schizophrenia has been questioned since then.^[14] A 2015 systematic review investigated the diagnostic accuracy of first rank symptoms:

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.^[16] These were retained in previous revisions largely for reasons of tradition, but had subsequently proved to be of little worth.^[7]

The ICD-10 defines seven sub-classifications of schizophrenia.^[8] These sub-classifications are:

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.^[17]

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).^[18]

People with schizophrenia often have additional mental health problems such as anxiety, depressive, or substance-use disorders.^[19] Schizophrenia occurs along with obsessive-compulsive disorder (OCD) considerably more often than could be explained by chance.^[20] 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.^[21][22][23] All of these factors result in an increased range of clinical presentations and suggest a significant etiological heterogeneity.^[19]

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.^[24] Females show more psychotic and affective symptoms than males, and have less social impairment. Men present more often with negative symptoms and disorganization.^[2] These differences are likely due to the protective effects of estrogen and are correlated with estrogen expression.^[25]

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".^[26]

Early-onset schizophrenia occurs before the age of 17^[27], and very-early onset schizophrenia occurs before the age of 13.^[28] late-onset occurs after the age of 40, and very-late-onset after the age of 60.^[29][30] It is estimated that 15% of the population with schizophrenia are late-onset and 5% very-late onset.^[29][30] 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.^[29][30]

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.^[31] Multiple genetic and environment factors have been associated with increased risk for developing schizophrenia.^[32] Furthermore, response to treatment with anti-psychotic medication is variable, with some patients being resistant to some therapies.^[33] Together, the differences in causes, response to treatment and pathophysiology suggest schizophrenia is heterogeneous from an etiological standpoint.^[34] The differences resulting from this in terms of in clinical manifestations make the disorder harder to diagnose.^[34]

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.^[35] 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.^[36] These factors complicate the use of genetic tests in diagnosis or prediction of the onset of schizophrenia.^[37]

If signs of disturbance are present for more than a month but less than six months, the diagnosis of schizophreniform disorder is applied.^[38] 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. Schizoaffective disorder is diagnosed if symptoms of mood disorder are substantially present alongside psychotic symptoms.

Psychotic symptoms may be present in several other mental disorders, including bipolar disorder,^[39] and borderline personality disorder.^[40] Delusions ("non-bizarre") are also present in delusional disorder, and social withdrawal in social anxiety disorder, avoidant personality disorder and schizotypal personality disorder. Schizophrenia cannot be diagnosed if symptoms of mood disorder are substantially present, or if symptoms of pervasive developmental disorder are present unless prominent delusions or hallucinations are also present. Schizophrenia is further complicated with obsessive-compulsive disorder (OCD), and it can be difficult to distinguish obsessions that occur in OCD from the delusions of schizophrenia.^[41] In children hallucinations must be separated from typical childhood fantasies.^[42]

A urine drug screen must be performed to determine if the cause for symptoms could be drug intoxication or drug-induced psychosis. For example, a few people withdrawing from benzodiazepines experience a severe withdrawal syndrome which may last a long time and can resemble schizophrenia.^[43] A general medical and neurological examination may also be needed to rule out medical illnesses which may rarely produce psychotic schizophrenia-like symptoms,^[38] such as metabolic disturbance, systemic infection, syphilis, HIV infection, epilepsy, and brain lesions. Stroke, multiple sclerosis, hyperthyroidism, hypothyroidism, and dementias such as Alzheimer's disease, Huntington's disease, frontotemporal dementia, and the Lewy body dementias may also be associated with schizophrenia-like psychotic symptoms.^[44] 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.