Issues with Reliability and Validity of Diagnosis

• Clinical Characteristics


  affects approx 1% of population globally.

  men - appear in late teens. women - late 20s
• DSM-V vs ICD-10


  DSM-V - states you need at least 1 positive symptom present

  ICD-10 - says 2 negative symptoms are sufficient. also includes subtypes of SZ such as paranoid SZ and catatonic SZ.
• Positive symptoms


  Hallucinations - auditory or visual

  Delusions - irrational beliefs/paranoid

  delusion of grandeur or persecution
• Negative symptoms


  Avolition - finding it difficult to being or keep up with goal directed activity.

  Andreason said there are 3 strains - lack of energy, lack of persistence in work/education and poor hygiene.

  Speech Poverty - reduction in amount and quality of speech.
• Type 1 vs Type 2 SZ

  Type 1 - characterised by positive symptoms. symptoms are an addition to the person.

  Type 2 - characterised by negative symptoms. symptoms where normal emotions are affected.
• Different types of SZ

  Catatonic - immobility or excessive motor activity.

  Paranoid - preoccupation with 1 or more delusion or frequent auditory hallucinations.

  Disorganised - must have disorganised speech and behaviour, flat or inappropriate affect that doesn't meet catatonic

  Undifferentiated - variation between symptoms.

  Residual - absence of prominent delusions or frequent auditory hallucinations
• Weakness - research done by Cheniaux et al

  had 2 psychiatrists independently diagnose 100 patients using both DSM-V and ICD-10 criteria.

  1 psychiatrist diagnosed 26 with SZ with DSM and 44 according to ICD-10

  other psychiatrist diagnosed 13 according to DSM and 24 according to ICD-10

  conclusion - inter-rate reliability is low.
• Weakness - research by Rosenhan

  7 volunteers -> no previous mental illnesses sent to 7 hospitals

  started hearing voices

  average 6.5mins spent with staff

  average 19 days

  all eventually diagnosed with SZ + bipolar -> none of them had the disorder.

  suggests that trained professionals aren't consistent in diagnosis
• Co-Morbidity/ Symptom Overlap


  Co-Morbidity

  Buckley et al concluded around 50% of patients with a diagnosis with SZ also had depression (50%) or substance abuse (47%)

  post traumatic stress occurred in 29% of cases and OCD in 23%

  shows SZ commonly occurs alongside other disorder so is co-morbid

  Symptom Overlap

  Ophoff et al assessed genetic material from 50,000 ppts.

  found 7 gene locations on genome associated with SZ, 3 were associated with bipolar disorder.

  suggests there's a genetic overlap, which may suggest genetic therapies might be developed to simultaneously treat different illnesses.
• Gender Bias/Culture Bias


  Gender Bias

  Luring + Powell randomly selected 290 men and women psychiatrists to read 2 cases of patient's behaviours.

  diagnosis -> when patients were described 56% of men and 20% of women were diagnosed with SZ.

  suggests diagnosis is influenced not only by gender of patient but also gender of clinician

  Culture Bias

  Copeland et al gave description of a patient to 134 US and 194 British psychiatrists.

  69% of US diagnosed SZ, only 2% of British diagnosed SZ -> questions reliability.

  Escobar - white psychiatrists may tend to overinterpret symptoms of black people during diagnosis.

  must pay more attention to the effects