Factors affecting reliability and validity

• Factors affecting reliability and validity in diagnosis and classification of SZ:

  • Co-morbidity
  • Culture
  • Gender bias
  • Symptom overlap
• Co-morbidity - the occurrence of two illnesses or conditions together
• Co-morbidity (AO1) Validity

  If conditions often occur together, this questions the validity of the diagnosis and classification because it can be hard to distinguish if the person has a single condition or more than one
• Co-morbidity (AO1) Reliability

  Affects reliability because different clinicians may diagnose different problems. Inter-rater reliability would be low.
• Co-morbidity (AO3)

  SZ is commonly diagnosed with other conditions - patients may also have issues with substance abuse, PTSD or OCD
• Co-morbidity (AO3)

  SZ and OCD are seen as two distinct conditions. Roughly 1% of the population develop SZ and roughly 2-3% develop OCD. Since both are fairly uncommon, we would expect only a few people with SZ to develop OCD

  However a meta analysis found that 12% of people with SZ displayed OCD symptoms - suggesting that diagnoses are either invalid or SZ is likely to be co-morbid with OCD
• Co-morbidity (AO3)

  Estimated that those with SZ, 50% of them have depression. If half SZ patients have depressions then it may be too difficult to distinguish between the two conditions. If very severe depression ooks like SZ and vice versa then they might be better seen as one condition
• Culture bias (AO1)

  People of Afro-Caribbean origin living in the UK are 7 times more likely than white people to be diagnosed with SZ but SZ rates in Africa are not high suggesting culture bias
• Culture bias (AO1)

  In African cultures, symptoms such as hearing voices may be more acceptable because of cultural beliefs in communication with ancestors and people are therefore more ready to report such experiences to a psychiatrist.

  More psychiatrists are white there experiences are more likely to be misinterpreted as bizarre and therefore overinterpreted as SZ
• Culture bias (AO3)

  Escobar has pointed out that white psychiatrists may tend to over interpret symptoms and distrust the honesty of black people during diagnosis. Supporting that there may be a culture bias in classification of SZ
• Culture bias (AO3)

  Fernando argues that people from ethnic minorities experience greater levels of racism, poverty etc and are likely to suffer SZ as a result. This could be the reason for higher rates found in Britain
• Culture bias (AO3) - Validity

  Culture bias is a threat to validity of classification as it suggests that it is confounded by cultural beliefs and behaviour or by stereotyping black patients by Mental Health Practitioners.
• Culture bias (AO3) - Reliability

  It also affects reliability as it suggests that non-white psychiatrists mat make a different diagnosis, so inter-rater reliability may be low
• Cultural bias (AO3)

  Bias in the classification of SZ could lead to the discrimination of Afro-Caribbean people, which may affect the ability to get or keep employment
• Gender bias (AO1)

  Longnecker et al reviewed studies of the prevalence of SZ and found that before 1980 there were equal numbers of diagnoses for males and females but since then, men are diagnosed far more than women
• Gender bias (AO3) - Validity

  If women are under diagnosed, the validity of the diagnosis is poor because it only works well on one gender.
• Gender bias (AO3) - reliability

  Inter-rater reliability would be poor as different clinicians may make different diagnoses based on whether they are affected by gender bias or not
• Gender bias (AO3)

  Loring and Powel asked 290 psychiatrists to read to patient case studies. When the patients were described as male, 56% of psychiatrists gave a diagnosis. Whereas if the patient was described as female only 20% were given a diagnosis.

  This shows evidence for gender bias in the classification and diagnosis of SZ
• Gender bias (AO3)

  Females tend to develop SZ between 4 and 10 years later than males and can develop a form or post-menopausal SZ suggesting there may be different types of SZ to which males and females are vulnerable, affecting the validity
• Gender bias (AO3)

  Having gender bias means that women may not receive the help and treatment that they need and that men may be receiving help and treatment that they don't need.
• Symptom overlap (AO1)

  There is considerable overlap of symptoms of SZ and other conditions.

  Both SZ and bipolar disorder can have the positive symptoms like delusions and negative symptom like avolition
• Symptom overlap (AO3) - validity

  Questions the validity. Under ICD patients might receive a diagnosis of SZ, however many of the same patients would receive a diagnosis of bipolar disorder under the DSM criteria
• Symptom overlap (AO3) - reliability

  Affects inter-rater reliability as two clinicians may come to different diagnoses
• Symptom overlap (AO3)

  Ketter reported that misdiagnosis due to symptom overlap can lead to years of delay in receiving treatment, during which time suffering and further degeneration can occur, as well as high levels of suicide.