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Reliability and Validity in Diagnosis and Classification of Schizophrenia

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Reliability and Validity in Diagnosis and Classification of Schizophrenia

Both the DSM (Diagnostic and Statistical Manual of Mental Disorders) and the ICD (International Statistical Classification of Diseases and Related Health Problems) require reliability and validity in diagnosing and classifying schizophrenia. Reliability and validity of diagnosis in psychology are essential for the DSM and ICD to be effective tools for psychiatrists to diagnose patients.

Schizophrenia is usually diagnosed between the ages of 20 to 30 for both men and women, although symptoms can appear long before then, sometimes even in early childhood.

Reliability and Validity in Diagnosis and Classification of Schizophrenia, Reliability and Validity Definition, StudySmarterReliability and validity definition, Tyler Smith - StudySmarter

How can we define reliability in diagnosis?

Reliability is the level of agreement that different psychiatrists can achieve on a single diagnosis for an individual, both over time and across cultures, provided that the disorder’s symptoms do not change.

  • It must be repeatable and consistent.

  • The diagnosis must be stable over time if the definition of the disorder has not changed.

To ensure a diagnosis and its classification are reliable, test-retest reliability is usually measured by the intraclass correlation (ICC) and the inter-rater reliability test, also measured as the kappa score. Both are statistical results that examiners can use to confirm the reliability of their results.

If the kappa classification has a score of 0.7 or more, it is considered reliable.

An example of test-retest reliability

To measure the reliability of something, the test-retest method is often used. In this method, a test is performed twice on one person at two different times.Lee et al. (2011) examined two tests used to measure switched and sustained attention in patients with schizophrenia for test-retest reliability.

  • The Symbol Digit Modalities Test (SDMT)
  • The Digit Vigilance Test (DVT)

147 Participants were tested with an interval of 1 week between tests. The results indicated both tests had good test-retest reliability and were stable measures. They both had high ICC values, a commonly used measure of test-retest reliability in studies.

An example of inter-rater reliability

Inter-rater reliability is when different psychiatrists should come to the same conclusion or diagnosis when diagnosing a person. The kappa score is a measure of inter-rater reliability.

In Cheniaux (2009), two psychiatrists had to assess 100 patients using the DSM and the ICD. They found that inter-rater reliability was poor, as one psychiatrist diagnosed 26 patients with schizophrenia using the DSM while diagnosing 44 patients with schizophrenia using the ICD.

As a result, schizophrenia is underdiagnosed or overdiagnosed depending on which system is used.

Similarly, Regier (2013) found the DSM edition at that time had a kappa score of 0.45, which is quite low and below the satisfactory requirement of 0.7, indicating a weakness in schizophrenia diagnosis.

Rosenhan (1973) schizophrenia study

Rosenhan’s (1973) study, one of the most influential studies affecting the diagnosis and treatment of psychiatric disorders today, highlighted the problems with reliability in the diagnosis of psychiatric disorders. Rosenhan emphasised that psychiatric hospital staff were somewhat desensitised and unaware of how drastic the experience of being admitted as a patient can be.In this study, Rosenhan himself and seven healthy individuals went to 12 different psychiatric hospitals.

  • These were three women and five men from various backgrounds, from psychologists to a painter. They used pseudonyms.

The pseudopatients asked the hospitals for an appointment and then complained upon arrival that they heard unfamiliar but same-sex voices, specifically:

  • Empty
  • Hollow
  • Thud

These words were explicitly chosen to show the pseudopatient has symptoms such as hallucinations, and to suggest that the pseudopatient believes their life is ‘empty and hollow’. The pseudopatients falsified their name, occupation, and profession to protect their identity. However, they were free to talk about their history and circumstances and were asked to present events from their life story as if they had happened.

Their history showed no signs of pathological problems.

Once admitted, the pseudopatients immediately ceased all symptomatic behaviours. They behaved as they normally would and talked to other patients and staff as they would have before they were admitted as pseudopatients. They were not told when they could leave the clinic. Instead, they were told they would have to convince the staff that they were sane to leave the clinic.

Pseudopatients who were asked how they were doing told staff they were fine and no longer had symptoms. They behaved accordingly and followed the rules. They also noted observations about the hospitals, secretly at first, but when it was obvious that no one cared or took note, they wrote them down without secrecy.

All but one of the patients were discharged with a diagnosis of schizophrenia in remission. Their length of stay ranged from 7 to 52 days (an average of 19 days). They were not classified as ‘sane’; the label of schizophrenia remained. The pseudopatients were not detected during their stay, although they remained sane throughout. There was a lack of adequate observation, but Rosenhan attributes this to a failure of the hospital rather than the patient and the lack of opportunity.

Interestingly, actual patients at the hospital recognised the pseudopatients as sane. About 35 of 118 patients recognised the sanity of the pseudopatients and even suggested their real occupation:

  • ‘You are not crazy. You are a journalist or a professor. You are checking out the hospital.’

Patients were more likely than staff to recognise normality, even though the pseudopatient insisted he was sick.

Rosenhah suspects this failure to recognise sanity is due to type 2 errors, also known as false-positive diagnoses. Rosenhan explained that diagnoses in this area of health care are neither useful nor reliable and represent a depressing and frightening reality that we must combat. Hospitals of this type cannot identify and treat these behaviours, and they also convey a sense of powerlessness.

Rosenhan stated:

We now know that we cannot distinguish sanity from insanity

The study impacted the way we treat patients with mental disorders today. It led to a condemnation of the use of institutionalised hospitals and a focus on care in the community.

Validity in classification and diagnosis of schizophrenia

Validity is the legitimacy of a test, i.e., whether what the psychiatrist uses to diagnose a person measures what it purports to measure.

If it is valid, the diagnosis represents something real and is different from other disorders.Cronbach and Meehl (1955) established several types of validity. For testing purposes, these are the most important to remember:

  • Construct validity – one can determine if a measurement instrument represents what it intends to measure.

  • Content validity – the test represents all construct areas, i.e., all areas of what one measures.

What are the issues with validity and reliability when diagnosing and classifying schizophrenia?

The following issues cause problems with validity and reliability:

  1. Comorbidity
  2. Symptom overlap
  3. Gender bias
  4. Culture bias

What is comorbidity?

Comorbidity is when two or more disorders coincide in a person.

It is not to be confused with symptom overlap.

Reliability and Validity in Diagnosis and Classification of Schizophrenia, Comorbidity, StudySmarterComorbidity in schizophrenia defined, Tyler Smith - StudySmarter

If two disorders can occur in one person, the validity of the diagnosis begs the question. Who is to say that it is only one disease and not several?Unfortunately, in the case of schizophrenia, there are many comorbidities with disorders such as OCD (obsessive-compulsive disorder) and depression. As a result, there are significant problems with the disorder’s validity.Buckley et al. (2009) found that comorbid depression occurs in 50% of patients with schizophrenia.

This finding raises some concerns:

  • Is it because psychiatrists or diagnostic manuals are poor at recognising the difference between these two disorders?

  • If they are so similar that there are problems with comorbidity, why can not they be considered a single disorder?

Since there is no truly distinct disorder, it is difficult to diagnose and treat schizophrenia with confidence.

Symptom overlap

Symptom overlap is the significant overlap between the symptoms of schizophrenia and other disorders.

Schizophrenia and bipolar disorder are good examples.Bambole et al. (2013) noted that patients diagnosed with schizophrenia and bipolar disorder have both positive and negative symptoms, making it difficult to distinguish between them.If these two disorders have too many symptoms in common, it questions the validity of the classification system and thus the validity of the diagnosis.For example, if a patient has these symptoms:

  • Avolition

  • Delusions of grandeur

The ICD may diagnose schizophrenia, while the DSM suggests bipolar disorder, indicating an apparent problem in the way these manuals claim to measure a disorder, and, therefore, a weakness in their validity.

Gender bias in diagnosing and classifying schizophrenia

Gender bias in the classification and diagnosis of schizophrenia occurs when the diagnosis is dependent on the patient’s gender. What symptoms they display and explain is usually irrelevant, as judgments are made based on their gender.

There may be gender-specific criteria, or there may be a bias based on stereotypes that the clinician believes in.

In the study by Loring and Powell (1988), 290 male and female psychiatrists were presented with two case studies of patient behaviour. When the patient was described as male, 56% of them were diagnosed with schizophrenia. However, only 20% diagnosed the patient as schizophrenic when described as female.There was a clear gender bias, but it was not present in the female psychiatrists when they made the diagnosis, suggesting that the gender of both the patient and the psychiatrist is a factor.

Longenecker (2010) found that more men than women have been diagnosed with schizophrenia since 1980.Are men genetically more prone to schizophrenia? Or do women function better in their daily lives than men with the disorder? If women present with the same symptoms but cope better because they have more support or continue to work and maintain relationships, there could be a bias among treating physicians and underdiagnosis in women.

Cotton et al. (2009) hypothesised that women cope better with their symptoms because they function better and may have more support. They function better on an interpersonal level and may not be diagnosed where men would be diagnosed with similar symptoms.Better interpersonal functioning may lead psychiatrists to underdiagnose women because the symptoms are masked and buried under-functioning routines. Some thus believe the case is too mild for a specific diagnosis, even though men would have been diagnosed with the same level of symptoms.

Cultural bias in diagnosing and classifying schizophrenia

Reliability and Validity in Diagnosis and Classification of Schizophrenia, Culture across the world, StudySmarterCulture across the world, icons made by flaticon.com/authors/flat-icons

Cultural bias exists because some psychiatrists diagnose a patient differently if the patient is from a different cultural background. They judge the patient according to what they think is acceptable in their own culture, rather than looking at the patient objectively and considering the patient’s culture and what is acceptable in the patient’s cultural views.

Tortelli et al. (2015) noted that despite improved study methods over time, there has been a higher rate of psychotic disorders in black, Caribbean ethnic groups in England over the past 60 years.

Ineichen et al. (1984) suggested people of West Indian origin were overdiagnosed with schizophrenia when assessed by white doctors in Bristol, possibly due to their ethnic background and culture.

Minsky et al. (2003) found African Americans were more likely to be diagnosed with the schizophrenic disorder than Latinos and European Americans.

Copeland (1971) also found that when a large group of psychiatrists from the US and the UK were presented with descriptions of a patient who exhibited certain behaviours and symptoms, 69% of US psychiatrists diagnosed the patient with schizophrenia, whereas only 2% of UK psychiatrists did so.

Why is that so?

  • There may be a cultural problem with understanding what is ‘normal’ behaviour because in some cultures, such as Africa, hearing voices and doing things that are normally considered positive symptoms of schizophrenia are more accepted than in other cultures where this is considered bizarre and irrational.

  • Racial biases could also play a role. When certain ethnic minorities are overdiagnosed compared to white people, especially by white psychiatrists, it indicates a high degree of miscommunication, bias, and lack of understanding of the patient and their symptoms.

  • Since countries of origin generally do not support these high rates of diagnosis, there is no genetic susceptibility. Why are African Americans in another country more likely to be diagnosed with schizophrenia than people in Africa and the West Indies?

Reliability and validity of diagnosis and classification of schizophrenia psychology

In light of the above, it is also important to acknowledge that:

  • No objective test for schizophrenia exists, as there is no biological basis to assess it. It can only be diagnosed by clinical interview, leading to the problems mentioned above. If bias and lack of reliability and validity exist, schizophrenia cannot be diagnosed with certainty.
  • Is it even a disorder if there are problems with reliability and validity?
  • When people are misdiagnosed, several problems arise, especially because schizophrenia has a stigma attached to it. Angermeyer and Matschinger (2003) surveyed adults of German nationality and found that labelling people with schizophrenia has a strong negative impact on public opinion.
  • In the case of misdiagnosis, treatment is likely to be ineffective because it does not address the root cause and does not properly treat symptoms.

Reliability and Validity in Diagnosis and Classification of Schizophrenia - Key takeaways

  • Reliability and validity are both key components of classification and diagnosing systems in psychology and are synonymous with successfully identifying and treating a person.
  • Reliability is the degree of agreement different psychiatrists can achieve on a single diagnosis for an individual, both over time and across cultures, provided the disorder symptoms do not change. It is about consistency.
  • Rosenhan demonstrated how diagnoses of mental disorders are not useful nor reliable in his 1973 study, where he and seven pseudopatients entered a hospital feigning hallucination symptoms, but upon entry, immediately behaved sanely. His study highlighted how stigmatising and unfair the nature of diagnoses can be, and how these hospitals were not able to distinguish sanity from insanity.
  • Validity is about the legitimacy of a test, whether what the psychiatrist uses to diagnose a person actually measures what it claims to measure. There are two main types of validity: construct and content validity.
  • Test-retest and inter-rater reliability tests ensure reliability.
  • Problems with validity occur when there are issues with comorbidity (two or more conditions within a person), symptom overlap (overlapping symptoms in a person across multiple conditions), gender bias, and cultural bias.

Frequently Asked Questions about Reliability and Validity in Diagnosis and Classification of Schizophrenia

The reliability of schizophrenia diagnosis depends on the psychiatrist diagnosing the person and the manual used. Overall, diagnosing schizophrenia reliably has improved over time as the guides have been revised, but some issues still require consideration, such as biases and issues with comorbidity and symptom overlap. 

Following the DSM or ICD by a certified, experienced psychiatrist would be the best, most reliable method to diagnose schizophrenia. However, both are still subject to biases, comorbidity, and symptom overlap.

Reliability is the level of agreement that different psychiatrists can achieve on a single diagnosis for an individual, both over time and across cultures, provided that the disorder’s symptoms do not change.


Validity is the legitimacy of a test, i.e., whether what the psychiatrist uses to diagnose a person measures what it purports to measure.

Multiple aspects can worsen schizophrenia, such as unstable, hostile households and family relationships (family dysfunctions), a lack of appropriate treatment, or not seeking treatment at all.

Schizophrenia is usually diagnosed between the ages of 20 to 30 for both men and women, although symptoms can appear long before then, sometimes even in early childhood.

Final Reliability and Validity in Diagnosis and Classification of Schizophrenia Quiz

Question

What is the definition of reliability in psychology?

Show answer

Answer

​​​​​Reliability is the level of agreement different psychiatrists can reach on a single diagnosis for one individual, across both time and cultures, given that there is no change in the symptoms of the disorder.

Show question

Question

What two tests can be used to test reliability?

Show answer

Answer

The test-retest and the inter-rater reliability tests can be used to determine reliability.

Show question

Question

What did Cheniaux (2009) find in their study?

Show answer

Answer

In Cheniaux (2009), two psychiatrists had to assess 100 patients using the DSM and the ICD. They found that inter-rater reliability was poor, as one psychiatrist diagnosed 26 patients with schizophrenia using the DSM while diagnosing 44 patients with schizophrenia using the ICD.

Show question

Question

What is the definition of validity in psychology?

Show answer

Answer

Validity is the legitimacy of a test, i.e., whether what the psychiatrist uses to diagnose a person measures what it purports to measure. If it is valid, the diagnosis represents something real and is different from other disorders.

Show question

Question

Name two types of validity in psychology.

Show answer

Answer

Construct validity and content validity.

Show question

Question

What is the definition of comorbidity?

Show answer

Answer

Comorbidity is when two or more disorders coincide in a person.

Show question

Question

What did Buckley et al. (2009) find in their study?

Show answer

Answer

Buckley et al. (2009) found that comorbid depression occurs in 50% of patients with schizophrenia.

Show question

Question

What is the definition of symptom overlap?

Show answer

Answer

Symptom overlap is the significant overlap between the symptoms of schizophrenia and other disorders.

Show question

Question

What did Bambole et al. (2013) find in their study?

Show answer

Answer

Bambole et al. (2013) noted that patients diagnosed with schizophrenia and bipolar disorder have both positive and negative symptoms, making it difficult to distinguish between them.

Show question

Question

What is the definition of gender bias?

Show answer

Answer

Gender bias in the classification and diagnosis of schizophrenia occurs when the diagnosis is dependent on the patient’s gender. What symptoms they display and explain is usually irrelevant, as judgments are made based on their gender.

Show question

Question

What did Longenecker (2010) find in their study?

Show answer

Answer

Longenecker (201) found that, since 1980, more men have been diagnosed with schizophrenia than women. This finding raises issues both in the diagnosis of women (whether under or overdiagnosed) and the overdiagnosis of men.

Show question

Question

What is the definition of cultural bias in psychology?

Show answer

Answer

Cultural bias exists because some psychiatrists diagnose a patient differently if the patient is from a different cultural background. They judge the patient according to what they think is acceptable in their own culture, rather than looking at the patient objectively and considering the patient’s culture and what is acceptable in the patient’s cultural views.

Show question

Question

What did Tortelli et al. (2015) find in their study?

Show answer

Answer

Tortelli et al. (2015) noted that despite improved study methods over time, there has been a higher rate of psychotic disorders in black, Caribbean ethnic groups in England over the past 60 years.

Show question

Question

If a disorder has issues with reliability and validity, what could that mean?

Show answer

Answer

It can mean the disorder may not be justified in being a diagnosable disease.

Show question

Question

What happens if a patient is misdiagnosed?

Show answer

Answer

Treatment may not be effective and will not address the root cause of the symptoms directly.

Show question

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