reliability and validity in diagnosis

Question 1

diagnosing sz

Answer 1

• DSM requires one positive symptom to be present, e.g. delusions or hallucinations
• ICD requires two or more negative symptoms to be present, e.g. avolition or speech poverty

Question 2

what is reliability?

Answer 2

• the extent to which a finding is consistent
• the extent to which psychiatrists can agree on the same diagnosis independently (inter-rater reliability)
• for a classification system to be reliable, the same diagnosis should be made each time

Question 3

what is validity?

Answer 3

• the extent we are measuring what we intend to measure
• consider the validity of the diagnostic tools: so different systems arrive at the same diagnosis for someone

Question 4

co-morbidity

Answer 4

• more than one disorder existing alongside a primary diagnosis
• when 2 conditions are diagnosed together it questions the validity of each’s classification
• the findings of research may be due to psychiatrists not being able to tell the difference between the 2
• if severe depression looks like schizophrenia or vice versa they may be better as a single condition

Question 5

what is one issue with positive symptoms?

Answer 5

• hallucinations or hearing voices may be more acceptable in african cultures due to beliefs about communication with ancestors
• when reported to a psychiatrist from another culture this may be seen as bizarre as they are culturally biased to what is normal in their culture, so are ethnocentric

Question 6

gender bias

Answer 6

• critics argue some diagnosis categories are biased toward pathologising one gender over the other
• gender bias also occurs as clinicians don’t consider that men have more negative symptoms than women and have higher levels of substance abuse, or that women have better recovery and lower relapse rates.
• clinicians also ignore that there are different risk factors between men and women, giving them different vulnerability levels during their life

Question 7

symptom overlap

Answer 7

• there is considerable overlap between the symptoms of schizophrenia and other conditions. e.g. schizophrenia and bipolar both share positive symptoms like delusions and negative symptoms like avolition. this questions the validity of the classification and diagnosis of schizophrenia

Question 8

limitation of diagnosis
1/4

Answer 8

cultural differences have been found within the diagnosis of sz. harrison et al (1984) found that those of west indian origin were over-diagnosed with sz by white doctors in bristol due to their ethnicity. also, copeland et al (1971) gave a description of a patient to 134 US and 194 british psychiatrists. 69% of the US psychiatrists gave a diagnosis of sz, compared to only 2% of the british. no research has been able to find a cause for this, suggesting that the symptoms of ethnic minorities are often misinterpreted. this indicates that the classification of sz is not cross-culturally applicable, and also calls into question the reliability of the diagnosis of sz as it highlights that patients can display the same symptoms but receive different diagnoses due to their ethnicity.

Question 9

limitation of diagnosis
2/4

Answer 9

research suggests the validity of the diagnosis of sz is low. in rosenhan’s (1973) study, 8 pseudopatients went into psychiatric hospitals, stating that they were hearing voices saying ‘empty’, ‘hollow’ and ‘thud’. all participants were admitted, and then stopped pretending their symptoms, instead behaving normally. on admission, staff diagnosed 11 with sz, and 1 with manic depression - their sanity was not detected. their behaviour was reported in the context of their new diagnosis, normal behaviour such as writing was suggested to be ‘pathological’. his research highlighted that psychiatrists cannot reliably distinguish between a sane and insane person, suggesting that measures used to detect and diagnose sz are flawed and have low validity.

Question 10

limitation of diagnosis
3/4

Answer 10

issue of gender bias when diagnosing sz, which is supported by loring and powell (1988). 290 male and female psychiatrists were randomly selected to read two case articles of patients behaviour and then offer a judgement using standard diagnostic criteria. when the patient was described as male or no information on gender was given, 56% were given a sz diagnosis. however when the patient was described as female, only 20% were given a diagnosis. this gender bias however was not evident among female psychiatrists - which suggests that the validity of the sz diagnosis is influenced by both the gender of the patient and the clinician

Question 11

limitation of diagnosis
4/4

Answer 11

issue of co-morbidity. beck (2009) found multiple other conditions with high co-morbidity rates with sz. e.g. depression with 50%, drug abuse with 47%, ptsd with 29% and ocd with 23%. these high rates can have many issues for patients, such as the complications of treatment plans, and also questions the validity of the classification of each separate condition. however, psychologists assessed people with co-morbid sz and cocaine abuse, and each separately. they found that despite symptom overlap, it was possible to make accurate diagnoses - symptom overlap and co-morbidity didn’t affect the validity of the diagnosis