Reliability and validity of diagnosing schizophrenia

What is reliability?

The consistency of measurements. We could expect to produce the same data if taken on successive occasions

What is reliability in context of diagnosing schizophrenia?

Ensuring the consistency in the diagnosis and classification of schizophrenia by different psychiatrists across time and cultures

What is validity?

Refers to whether an observed effect is a genuine one

What is validity in the context of diagnosing and classifying schizophrenia?

Ensuring that the patient is receiving a correct diagnosis of schizophrenia has been correctly classified

What are two factors which brings into question the reliability of diagnosing schizophrenia?

1. Cultural differences

2. Inter-rater reliability

What are three factors which bring into question the validity of schizophrenia?

1. Symptom overlap

2. Co-morbidity (linked to issues with classification)

3. Gender bias

What is co-morbidity?

The extent that two (or more) conditions or diseases occur simultaneously in a patient. E.g. a patient having both schizophrenia and depression

This brings into question the classification of schizophrenia as if it is commonly found alongside another disorder it may not be a separate condition

What is symptoms overlap?

Symptoms of a disorder may not be unique to that disorder but may also be found in other disorders, making accurate diagnosis difficult

How do cultural differences affect reliability of diagnosing schizophrenia?

Hearing voices may be more acceptable in African cultures such as Ghana due to cultural beliefs in communication with ancestors - schizophrenia may be inconsistently diagnosed between cultures

What is inter-rater reliability in relation to the diagnosis of mental health disorders?

The extent to which two or more mental health professionals arrive at the same diagnosis for the same patients

How does inter-rater reliability affect reliability of diagnosing schizophrenia?

Schizophrenia has been show to have poor inter-rater reliability.

Whaley (2001) found that inter-rater reliability of 0.11

List and outline another 2 examples of studies which support the lack of inter-observer reliability diagnosing SZ

Cheniauz et al (2009) had 2 psychiatrist independently diagnose 100 patients using both DSM and ICD criteria and found ICD more likely to lead to a diagnosis

Rosenhan (1973) Being sane in insane places: ‘ normal’ people presented themselves to psychiatric hospitals in the US claiming they head and unfamiliar voice in their head saying the words ‘empty, hollow, thud’

How does gender bias affect validity of diagnosing schizophrenia?

Accuracy of a diagnosis is dependent on the gender of the individual

This is as males are more likely to be diagnosed than females as females appear to function better - means schizophrenia could be unrecognised in females

List and outline studies exhibiting cultural differences in diagnosing SZ:

Cochrane (1977): reported that the incidence of schizophrenia in the West Indies and the UK is 1% but that people of African-Caribbean origin are seven times more likely to be diagnosed with schizophrenia when living in the UK

Copeland (1971): Gave 134 US and 194 British Psychiatrists details of a patient. 69% US diagnosed patient with SZ, whereas only 2% of British ones gave the same diagnosis

Outline the study that exhibits co-morbidity in the diagnosis of SZ:

Buckley et al (2009)

• 50% of patients with schizophrenia also have a diagnosis of depression

• 47% also diagnosed with substance abuse

• 29% also have PTSD

• 23% also have OCD

List and outline the 3 studies which show symptom overlap in diagnosing SZ:

Ellason et al (1995): Claimed that dissociative identity disorder (DID) has more schizophrenic symptoms than people diagnosed with schizophrenia

Loring and Powell (1988): Selected 290 male and female psychiatrists to read two case studies of patients behaviour. When patients were described as ‘males’, 56% of the psychiatrists gave a lot diagnosis of schizophrenia, when described as ‘female’, only 20% were given a diagnosis

Cotton et al (2009): Highly functioning women may not receive a diagnosis - better interpersonal functioning may bias practitioners to under diagnose SZ

What part of the brain being overactive leads to patients hearing voices?

Brocas area