Reliability and Validity in Diagnosis & Classification of Schizophrenia

Describe reliability in diagnosis and classification of schizophrenia

Reliability:

• Consistency in the diagnosis

• Whether there is agreement in the diagnosis of schizophrenia by different psychiatrists - inter-rater reliability

• Whether diagnostic tests are consistent on different occasions - test-retest reliability

There is a criticism that DSM and ICD tools are routinely used with a high level of reliability by mental health clinicians. Describe how this is a weakness of reliability.

• Cheniaux (2009):

  • Asked two psychiatrists to independently diagnose 100 patients using both the DSM and ICD

  • Inter-rater reliability was poor - e.g., using the DSM, one psychiatrist diagnosed 26 patients with schizophrenia whilst the other only diagnosing 13

• This is a weakness of the diagnostic systems as they failed to produce consistent results and therefore shows that the reliability of diagnosing schizophrenia is poor

DSM and ICD tools are routinely used with a high level of reliability by mental health clinicians. Describe a counterargument of this

• Research has found that reliability for diagnosis in schizophrenia has improved

  • Osario et al (2019) reported excellent reliability for the diagnosis of schizophrenia using the DSM-5

  • Pairs of interviewers achieved inter-rater reliability =.97 and test-retest reliability =.92

  • This suggests that the diagnostic system is consistently applied and therefore has good reliability

Describe and define co-morbidity

• The presence of one or more additional disorders or diseases simultaneously occurring with schizophrenia

• People with schizophrenia also commonly suffer with the following conditions:

  • Substance abuse - 47%

  • Anxiety/panic disorder - 15%

  • Symptoms of depression - 50%

• Suffers experiencing simultaneous disorders suggests that schizophrenia may not actually be a separate disorder leading to different medical professionals giving different diagnoses of the same patient

There is lots of evidence to suggest that many sufferers also have issues of substance abuse. Describe how this is a strength of co-morbidity

• Buckley (2009) - around 50% of patients with schizophrenia also have depression or substance abuse

  • Alcohol and cannabis are substances that can be abused by people with schizophrenia (maybe as a way of self-medicating)

• This makes a reliable diagnosis difficult but also leads to lower levels of functioning and increased hospitalisations - making effective treatment difficult to achieve

• It may also lead to lower compliance with medication

• This is a strength as it demonstrates the complexities involved in giving a reliable diagnosis if the person is also using recreational drugs - it’s difficult to know what symptoms are a direct effect of having schizophrenia or substance abuse

Describe how cultural bias affects the validity of classification and diagnosis of schizophrenia

• The extent to which the diagnostic system reflects beliefs about what is viewed as normal and acceptable in Western and predominantly white cultures

• This reduces the validity of the diagnostic system

• The ICD and DSM were developed by Western clinicians and criticised for lacking cultural relativism

  • People show behaviours such as hearing voices (which may be normal in their own culture) are sometimes classified as having schizophrenia

Describe how cultural bias affects the reliability of classification and diagnosis of schizophrenia

• Research suggests there is a significant variation between culture when it comes to diagnosing schizophrenia

  • Copeland (1971) gave 134 US and 194 British psychiatrists a description of a patient

  • 60% of US psychiatrists diagnosed schizophrenia but only 2% of British ones did - showing that diagnosis was unreliable across different cultures

Research suggests that the diagnosis of schizophrenia is affected by culture bias. Describe how this is a weakness of culture bias on the diagnosis of schizophrenia

• Pinto and Jones (2008): some people believe voices are communications from ancestors in Haitii

  • British people of African-Caribbean origin are up to nine times more likely to be diagnosed than white British people - although people living in African-Caribbean countries are not

• Higher statistics could represent the effect of poorer housing and higher rates of unemployment in minority groups such as African-Caribbean groups

• This is a weakness of the diagnostic system as it highlights that the difference is due to biased over interpretations of symptoms by some psychiatrists

Describe validity in the diagnosis and classification of schizophrenia

• The extent to which methods used to measure schizophrenia are accurately measuring schizophrenia

  • E.g, patients may have hallucinations but is not suffering with schizophrenia or psychiatrists may be misinterpreting the behaviour of the patient

• Validity can be assessed using predictive validity - if a diagnosis leads to successful treatment then it is valid

• Findings from research into the validity of diagnosis of schizophrenia is mixed

  • Some researchers report that when you match patients diagnosed with schizophrenia to the DSM criteria there is good correlation (Hollis 2000)

The same way people rarely share the same symptoms, there is no evidence they share the same outcomes. Describe how this is a weakness of validity in diagnosis of schizophrenia

• The prognosis for patients diagnosed with schizophrenia is as follows:

  • 20% recovering their previous level of functioning

  • 10% achieving significant and lasting improvement

  • 30% showing some improvement with intermittent relapses

• This is a weakness since it suggests diagnosis has little predictive validity because some people never appear to recover from the disorder while many do

Describe the effects of gender bias on the diagnosis and classification of schizophrenia

• Accuracy of diagnosis is dependent on the gender of an individual

  • Diagnostic criteria may be gender-biased or clinicians may base their judgments on stereotypical beliefs about gender

• Since the 1980s - men are diagnosed with schizophrenia more often than women

  • This may be likely due to women having more support around them and functioning better than men

• Cotton (2009) - female patients with schizophrenia function better than male patients e.g., they are more likely to work and have good relationships

Research suggests that gender bias is a problem in the diagnosis of schizophrenia and subsequent treatment offered. Describe how this is a weakness of the effect of gender bias on the classification and treatment of schizophrenia

• Evidence shows that males could be more likely to be committed to psychiatric institutions when they show mild symptoms of schizophrenia due to the risk of socially deviant behaviour

• Females are likely to be voluntary patients because they are more likely to seek help earlier

• This is a strength as it supports the idea that gender differences in diagnosis exist and women’s better interpersonal functioning may bias clinicians to under-diagnose them

  • This threatens the validity of the diagnostic system because people may get an incorrect or no diagnosis based on their gender

Describe the effect of symptom overlap on the diagnosis and classification of schizophrenia

• When symptoms of schizophrenia are also found in other disorders

  • E.g., positive symptoms such as delusion and negative symptoms such as avolition occur in both schizophrenia and bipolar disorder

• This makes it difficult for clinicians to accurately decide which particular disorder someone is suffering from when diagnosing

Research suggests that symptom overlap can cause issues when accurately and reliably diagnosing schizophrenia. Describe how this is a weakness of the effects of symptom overlap in the diagnosis and classification of schizophrenia

• Ophoff (2011) found a genetic overlap between bipolar disorder and schizophrenia

  • 3 of the 7 gene locations on the genome associated with schizophrenia were also associated with bipolar disorder

  • Both schizophrenia and bipolar disorder involve positive symptoms and negative symptoms

• This is a weakness as it suggests that it is difficult to distinguish schizophrenia from other illnesses and that schizophrenia & bipolar disorder are not 2 different conditions but variations of a single condition