Diagnosis of schizophrenia

Diagnosis of schizophrenia is the decision of a doctor when they meet someone. While the doctor is with someone they watch and listen to what someone is doing to decide if they have a schizophrenia (sz) problem. Doctors make a decision using their senses.
In the past
In the 1911 publication of Dr Bleuler, sz is diagnosed by recognition of "large symptom-complexes", one of which "peculiar association disturbance" is always a symptom that exists for diagnosis to be made, examples of this are "blocking" and "spliting of ideas". The Fundamental symptoms are present in every diagnosed case, the Accessory symptoms are present also in other illnesses.  The "key" symptom is the association disorder Burkhart Brückner, Ansgar Fabri (2015) Bleuler, Paul Eugen. : "Research on schizophrenia" In: Biographical Archive of Psychiatry.  (retrieved:10.11.2023)

The fundamental symptoms of Dr Bleuler were:
disturbances of association and affectivity 
a liking, https://dictionary.cambridge.org/dictionary/english/predilection preference,  https://www.thefreedictionary.com/predilection ("prediliction") for fantasy against reality 
the inclination to "divorce" from reality (autism) 
A past definition of the most important symptoms of sz, which are described as the "First-Rank Symptoms" were described by Kurt Schneider during 1938 Schneiderian first- and second-rank symptoms Oxford Reference these are: 
positive symptoms: auditory hallucinations; thought withdrawal, insertion and interruption; thought broadcasting; somatic hallucinations; delusional perception; feelings or actions as made or influenced by external agents Karla Soares‐Weiser, Nicola Maayan, Hanna Bergman, Clare Davenport, Amanda J Kirkham, Sarah Grabowski, Clive E Adams, and Cochrane Schizophrenia Group First rank symptoms for schizophrenia First rank symptoms for schizophrenia
negative symptoms: deficits of emotional responses or other thought processes 

How a decision is made
To decide if a person has schizophrenia  
a doctor uses The Diagnostic and Statistical Manual of Mental Disorders (DSM) DSM-IV to DSM-5 Schizophrenia Comparison Substance Abuse and Mental Health Services Administration.
Rockville (MD): Substance Abuse and Mental Health Services Administration (US); 2016 June  
made by the American Psychiatric Association ICD vs. DSM October 2009, Vol 40, No. 9 American Psychological Association 
for the United States of America (US) Ellen Doernberg, Eric Hollander (2016) Neurodevelopmental Disorders (ASD and ADHD): DSM-5, ICD-10, and ICD-11 CNS Spectrums, 21(4), 295-299. 01 July 2016  doi:10.1017/S1092852916000262 
and the International Classification of Diseases (ICD),   
made by World Health Assembly and the  World Health Organisation,  
for all of the world,  
although used in the US with a US only version made by The Centers for Disease Control and Prevention (CDC) because of the different cultures. Freddy A. Paniagua ICD-10 Versus DSM-5 on Cultural Issues SAGE Open, 8(1). https://doi.org/10.1177/2158244018756165  

Criteria for diagnosisThe DSM diagnostic description, of edition 5, which current of 2023, for only the first meeting between a person with a problem and a doctor, is:

A. Two (or more) of the following, each present for a significant portion of time during a 1-month period (or less if successfully treated). At least one of these must be (1), (2), or (3):

1. delusions	

2. hallucinations	

3. disorganized speech (e.g., frequent derailment or incoherence)	 

4. grossly disorganized or catatonic behavior	

5. Negative symptoms (i.e., diminished emotional expression or avolition).

B. For a significant portion of the time since the onset of the disturbance, level of functioning in one or more major areas, such as work, interpersonal relations, or self-care, is markedly below the level achieved prior to the onset (or when the onset is in childhood or adolescence, there is failure to achieve expected level of interpersonal, academic, or occupational functioning).

C. Duration: Continuous signs of the disturbance persist for at least 6 months. This 6-month period must include at least 1 month of symptoms (or less if successfully treated) that meet Criterion A (i.e., active-phase symptoms) and may include periods of prodromal or residual symptoms. During these prodromal or residual periods, the signs of the disturbance may be manifested by only negative symptoms or two or more symptoms listed in Criterion A present in an attenuated form (e.g., odd beliefs, unusual perceptual experiences).

D. Schizoaffective disorder and depressive or bipolar disorder with psychotic features have been ruled out because either (1) no major depressive or manic episodes have occurred concurrently with the active-phase symptoms, or (2) if mood episodes have occurred during active-phase symptoms, they have been present for a minority of the total duration of the active and residual periods of the illness.

E. The disturbance is not attributable to the physiological effects of a substance (e.g., a drug of abuse, a medication) or another medical condition.

F. If there is a history of autism spectrum disorder or a communication disorder of childhood onset, the additional diagnosis of schizophrenia is made only if prominent delusions or hallucinations, in addition to the other required symptoms of schizophrenia, are also present for at least 1 month (or less if successfully treated).

For the ICD (not the CDC changed description), which is the 11th version, current of 2023: 

At least two of the following symptoms must be present (by the individual’s report or through observation by the clinician or other informants) most of the time for a period of 1 month or more. At least one of the qualifying symptoms should be from item a) through d) below:

a. Persistent delusions (e.g., grandiose delusions, delusions of reference, persecutory delusions).

b. Persistent hallucinations (most commonly auditory, although they may be in any sensory modality).

c. Disorganized thinking (formal thought disorder) (e.g., tangentiality and loose associations, irrelevant speech, neologisms). When severe, the person’s speech may be so incoherent as to be incomprehensible (‘word salad’).

d. Experiences of influence, passivity or control (i.e., the experience that one’s feelings, impulses, actions or thoughts are not generated by oneself, are being placed in one’s mind or withdrawn from one’s mind by others, or that one’s thoughts are being broadcast to others).

e. Negative symptoms such as affective flattening, alogia or paucity of speech, avolition, asociality and anhedonia.

f. Grossly disorganized behaviour that impedes goal-directed activity (e.g., behaviour that appears bizarre or purposeless, unpredictable or inappropriate emotional responses that interferes with the ability to organize behaviour.)

g. Psychomotor disturbances such as catatonic restlessness or agitation, posturing, waxy flexibility, negativism, mutism, or stupor. Note: If the full syndrome of Catatonia is present in the context of Schizophrenia, the diagnosis of Catatonia Associated with Another Mental Disorder should also be assigned.

Differential diagnosis
There are no medical tests that can be used to say if a person has sz or not, so getting a diagnosis depends on which list of symptoms are used. It also depends on the doctor or psychologist who talks to the person. Some scientists think that sz is several separate illnesses that have some of the same symptoms. These scientists claim that the research done on sz is not accurate since different researchers mean different things when they use the word "schizophrenia" in scientific studies. Similarly named mental illnesses include schizotypal personality disorder, schizoaffective disorder, and schizoid personality disorder.

Unlike what the name suggests, people with sz do not have a split personality.

Splitting also occurs in Borderline Personality Disorder. Scott O. Lilienfeld, Katheryn C. Sauvigné, Steven Jay Lynn, Robin L. Cautin, Robert D. Latzman, Irwin D. Waldman Fifty psychological and psychiatric terms to avoid: a list of inaccurate, misleading, misused, ambiguous, and logically confused words and phrases (34) Splitting Front. Psychol., 03 August 2015 Sec. Educational Psychology Volume 6 - 2015 | https://doi.org/10.3389/fpsyg.2015.01100Ondrej Pec, Petr Bob, Jiri Raboch Splitting in Schizophrenia and Borderline Personality Disorder March 6, 2014 https://doi.org/10.1371/journal.pone.0091228
The praecox feeling
A study of 2018 found that some doctors, perhaps many,  diagnose sz within the first few minutes Marcin Moskalewicz , Michael Schwartz , Tudi Gozé Phenomenology of Intuitive Judgment: Praecox-Feeling in the Diagnosis of Schizophrenia AVANT, Vol. IX, No. 2/2018  avant.edu.pl/en based on the  "praecox feeling". Tudi Gozé How to Teach/Learn Praecox Feeling? Through Phenomenology to Medical Education Front Psychiatry. 2022; 13: 819305. Published online 2022 Mar 18. doi: 10.3389/fpsyt.2022.819305 The "feeling" is perhaps like first impressions. Matthew Rabin, Joel L. Schrag First Impressions Matter: A Model of Confirmatory Bias The Quarterly Journal of Economics, Volume 114, Issue 1, February 1999Philip E. Tetlock Accountability and the Perseverance of First Impressions Social Psychology Quarterly Vol. 46, No. 4 (Dec., 1983) American Sociological AssociationOmri Gillath, Angela J. Bahns, Fiona Ge, Christian S. Crandall Shoes as a source of first impressions Journal of Research in Personality Volume 46, Issue 4, August 2012Harris, M. J., & Garris, C. P. (2008). You never get a second chance to make a first impression: Behavioral consequences of first impressions. In N. Ambady & J. J. Skowronski (Eds.), First impressions (pp. 147–168). Guilford Publications. American Psychological Association The "praecox feeling" is not in the  "symptom checklists" of DSM and ICD   which are intended for use by psychiatrists for diagnosis.

Other problems that go with sz
Additional problems as defined by clinicians and medical services are described in medical terms as "comorbidities". One research group found "substance misuse" was mostly the morbidity which people with sz had; Peter F. Buckley, Brian J. Miller, Douglas S. Lehrer, David J. Castle Psychiatric Comorbidities and Schizophrenia Schizophrenia Bulletin, Volume 35, Issue 2, March 2009, Pages 383–402, https://doi.org/10.1093/schbul/sbn135 Published: 14 November 2008 substances are known as psychoactive Rassool GH (2012)  Substance misuse in older people 1: types of substance misuse and risk factors. Nursing Times [online]; 108: 30/31, 12-14.  
References

Category:Schizophrenia