Diagnosis and classification of schizophrenia

• Diagnosing:

  • clincian has to use diagnosis manual - international classification of disease (ICD-11) or diagnostic statistical manual (DSM-5)
  • previous editions recognise subtypes of schizo (paranoid) but were found inconsistent
• DSM criteria:

  • 2 or more characteristics - positive or negative
  • social/occupational dysfunction for long time
  • duration - continuous disturbances for at least 6 months
  • schizoaffective + depressive/bipolar ruled out
  • disturbances not attributable to substance abuse
• positive symptoms:

  • additional experiences beyond ordinary existence
  • hallucinations and delusions
• hallucinations:

  • unusual sensory experiences - visual, auditory, tactile, olfactory
• delusions: irrational beliefs

  • paranoia - being followed/persecuted by government
  • delusions of grandeur - superpowers
  • delusions of reference - personal messages through TV, news
• negative symptoms:

  • reduction or loss of usual abilities and experiences
  • speech poverty + avolition
• speech poverty (alogia):

  • decrease in amount + quality of speech
  • know words but cant spontaneously produce
• avolition:

  • apathy - lack of interest/enthusiasm/concern
  • lack of goal directed behaviour e.g reduced motivation
  • poor hygiene, lack of energy, lack of persistence in work
• reliability:

  • consistency of system to asses particular symptoms
  • clinicians must reach same conclusion at 2 different times (test/retest) + be consistent between clincians (interrate)
• validity:

  • extent that diagnosis represents something real + distinct from other disorders
  • systems measures what it intends to measure
• reliability research:

  • whaley - inter rate correlations for DSM3 +0.11
  • osario et al - +0.97 +0.92 for test/retest for DSM5
• validity research:

  • chineux et al - 2 psychiatrists assessed same 100 clients using DSM4 + ICD10, 68 diagnosed under ICD, 39 under DSM - schizophrenia over/under diagnosed (low criterion validity)
  • osario et al - excellent agreement between clinicians when using DSM - criterion validity high when it takes place within a single diagnostic system
• factors that affect reliability + validity:

  • co morbidity
  • symptom overlap
  • gender bias
  • culture bias
• co morbidity: extent that 2 or > conditions occur

  • buckley et al - 50% diagnosed have depression, 47% with substance abuse, 23% with OCD
  • classification = schizophrenia may not exist as distinct condition
  • diagnosis = some may have unusual cases of other conditions, misdiagnosis
• symptom overlap: symptoms may be found in other conditions

  • Ellason + Ross - people with DID have more schizo symptoms
  • most people diagnosed have sufficient symptoms for other disorders
  • classification = schizo, bipolar, DID may be variations of single condition
  • diagnosis = difficult to distinguish from other disorders
• gender bias:

  • loring + powell - 56% given diagnosis when male, 20% women - was only evident in male psychiatrist, affected by gender + clincian
  • longenecker et al - since 80s men diagnosed more, women function better with disorder - leads to underdiagnosis as women not recieving correct services
• culture bias:

  • copeland - 69% US diagnosed, 2% UK using same description
  • luhrmann et al - interviewed patients from ghana, india + US about hearing voices - US more likely to report violent voices, other cultures believe it's messages from ancestors