Classification and diagnosis of schizophrenia
Reliability and validity
● Reliability refers to how consistent results are using the tool e.g. diagnostic criteria
in the DSM-V or ICD-11.
● Inter-rater reliability is the measure of how two observers agree e.g. two doctors
diagnose the same person with schizophrenia.
○ Test-retest reliability is where the same doctor gives the same diagnosis to
the same individual with the same symptoms over time.
● Low reliability indicates low validity.
○ If reliability is low then it indicates that the individual does not have
schizophrenia or that schizophrenia is not a real disorder with clear and
unique symptoms.
● Beck 1963 reviewed 153 pts diagnosed by multiple doctors and only found a 54%
concordance rate suggesting low inter-rater reliability and may result in improper
treatment.
● Osiris 2019 reported inter-rather reliability of 0.97 and test-retest reliability of 0.92
using the DSM-V suggesting reliability of diagnoses has improved.
Gender bias
● Gender bias refers to how diagnosis accuracy is affected by a pt’s gender.
○ Diagnoses may vary because of a clinician's prejudices and views and beliefs
about gender.
● Men and women are equally diagnosed over a lifetime but men generally diagnosed
5 years earlier than women.
● Men are also more likely to have comorbid substance abuse and suffer negative
symptoms.
○ Women are more likely to display positive symptoms. This may lead to
misdiagnosis for disorders like bipolar where there is greater symptom
overlap.
● Cotton et al suggested that women typically function better than men, more likely to
work and have good family relationships.
○ This explains why women are underdiagnosed as they hide their symptoms
better than men.
● Fischer and Buchanan found a 1.4:1 ratio of men to women diagnosed with sz
● Loring and Powell gave 290 psychiatrists identical case studies: w/m, w/f, b/m, b/f.
○ Over-diagnosis of black cases and under-diagnosis of female cases.
○ Most accurate when gender and race of psychiatrist same as pt.
Culture bias
● Culture bias refers to how symptom may be interpreted differently by different
cultures.
, ● Fearon found that Afro-Caribbeans and African-Americans in the UK and US are 10
times more likely to be diagnosed with sz compared to the 1% in general population.
○ Could be because hallucinations, such as angelic voices or voices of past
ancestors, in those cultures are seen as something special and normal and
not a sign of mental disorder.
● This is because western definitions and ideals of mental health (in DSM and ICD) are
applied to non-western cultures.
Co-morbidity
● Comorbidity refers to the extent that 2 or more conditions can exist at the same time.
● Schizophrenia is often diagnosed with other disorders such as depression and
substance abuse/addiction.
○ Can lead to inaccurate diagnoses as it may just be a severe case of
depression.
○ Their tendency to be comorbid may suggest they are not separate disorders.
● Buckley found sz comorbidity with: depression 50%, drug abuse 47%, PTSD 29%,
OCD 23%.
○ Complicates treatment plans which may lead to worse condition.
○ Suggests these diagnoses are not separate disorders and should be
classified under one umbrella.
Symptom overlap
● Symptom overlap refers to how symptoms of schizophrenia are also present in other
disorders.
● Positive symptoms like delusions and hallucinations are commonly seen in bipolar
disorder.
○ If symptoms are so similar it may be that they are one disorder or are not
clearly defined.
○ Can lead to misdiagnosis and issues with inter-rater reliability.
● Ellison and Ross found people with dissociative identity disorder have more
schizophrenic symptoms than people with schizophrenia.
● Swets et al found 12% of sz pts fulfilled criteria for OCD and 25% displayed
obsessive-compulsive symptoms.
Reliability and validity
● Reliability refers to how consistent results are using the tool e.g. diagnostic criteria
in the DSM-V or ICD-11.
● Inter-rater reliability is the measure of how two observers agree e.g. two doctors
diagnose the same person with schizophrenia.
○ Test-retest reliability is where the same doctor gives the same diagnosis to
the same individual with the same symptoms over time.
● Low reliability indicates low validity.
○ If reliability is low then it indicates that the individual does not have
schizophrenia or that schizophrenia is not a real disorder with clear and
unique symptoms.
● Beck 1963 reviewed 153 pts diagnosed by multiple doctors and only found a 54%
concordance rate suggesting low inter-rater reliability and may result in improper
treatment.
● Osiris 2019 reported inter-rather reliability of 0.97 and test-retest reliability of 0.92
using the DSM-V suggesting reliability of diagnoses has improved.
Gender bias
● Gender bias refers to how diagnosis accuracy is affected by a pt’s gender.
○ Diagnoses may vary because of a clinician's prejudices and views and beliefs
about gender.
● Men and women are equally diagnosed over a lifetime but men generally diagnosed
5 years earlier than women.
● Men are also more likely to have comorbid substance abuse and suffer negative
symptoms.
○ Women are more likely to display positive symptoms. This may lead to
misdiagnosis for disorders like bipolar where there is greater symptom
overlap.
● Cotton et al suggested that women typically function better than men, more likely to
work and have good family relationships.
○ This explains why women are underdiagnosed as they hide their symptoms
better than men.
● Fischer and Buchanan found a 1.4:1 ratio of men to women diagnosed with sz
● Loring and Powell gave 290 psychiatrists identical case studies: w/m, w/f, b/m, b/f.
○ Over-diagnosis of black cases and under-diagnosis of female cases.
○ Most accurate when gender and race of psychiatrist same as pt.
Culture bias
● Culture bias refers to how symptom may be interpreted differently by different
cultures.
, ● Fearon found that Afro-Caribbeans and African-Americans in the UK and US are 10
times more likely to be diagnosed with sz compared to the 1% in general population.
○ Could be because hallucinations, such as angelic voices or voices of past
ancestors, in those cultures are seen as something special and normal and
not a sign of mental disorder.
● This is because western definitions and ideals of mental health (in DSM and ICD) are
applied to non-western cultures.
Co-morbidity
● Comorbidity refers to the extent that 2 or more conditions can exist at the same time.
● Schizophrenia is often diagnosed with other disorders such as depression and
substance abuse/addiction.
○ Can lead to inaccurate diagnoses as it may just be a severe case of
depression.
○ Their tendency to be comorbid may suggest they are not separate disorders.
● Buckley found sz comorbidity with: depression 50%, drug abuse 47%, PTSD 29%,
OCD 23%.
○ Complicates treatment plans which may lead to worse condition.
○ Suggests these diagnoses are not separate disorders and should be
classified under one umbrella.
Symptom overlap
● Symptom overlap refers to how symptoms of schizophrenia are also present in other
disorders.
● Positive symptoms like delusions and hallucinations are commonly seen in bipolar
disorder.
○ If symptoms are so similar it may be that they are one disorder or are not
clearly defined.
○ Can lead to misdiagnosis and issues with inter-rater reliability.
● Ellison and Ross found people with dissociative identity disorder have more
schizophrenic symptoms than people with schizophrenia.
● Swets et al found 12% of sz pts fulfilled criteria for OCD and 25% displayed
obsessive-compulsive symptoms.
