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• Schizophrenia (SZ)


  A serious mental disorder found in about 1% of the population, and doesn't have a single defining characteristic, but is a cluster of symptoms of which appear to be unrelated
• Major systems for the classification and diagnosis of mental disorders

  • The World Health Organisation's International Classification of Disease 11 (ICD-11)
  • The American Psychiatric Association's Diagnostic and Statistical Manual Edition 5 (DSM-5)
• Difference between ICD-11 and DSM-5 in classifying Schizophrenia

  DSM-5 states that at least 1 positive symptom must be present for diagnosis, while ICD-11 states 2 or more negative symptoms are sufficient for a diagnosis
• Previous subtypes of schizophrenia that have been removed from both DSM & ICD

  • Paranoid Schizophrenia
  • Hebephrenic schizophrenia
  • Catatonic schizophrenia
• Positive symptoms


  An added behaviour that wouldn't be there in someone without SZ
• Negative symptoms


  A behaviour that would be found in someone without SZ missing in the person with SZ
• Positive symptoms


  • Delusions
  • Hallucinations
• Delusions


  False beliefs that are firmly held despite being completely irrational, or for which there is no evidence
• Types of delusions


  • Delusions of Persecution
  • Delusions of Grandeur
  • Delusions of Control
• Hallucinations


  False perceptions that have no basis in reality
• Types of hallucinations


  • Auditory
  • Smell
  • Touch
  • Sight
• Avolition


  Difficulty or inability to start and continue with goal-directed behaviour
• Speech Poverty


  Reduction in the amount and quality of speech, characterised by lack of ability to produce fluent words
• Inter-rater reliability


  The extent to which psychiatrists can agree on the same diagnosis when independently assessing patients
• Validity


  The extent to which we are measuring what we are intending to measure
• Rosenhan (1973) showed that healthy 'pseudopatients' could gain admission to psychiatric hospital by pretending to have auditory hallucinations
• Once in the hospital, the staff interpreted the behaviours of the pseudopatients, who were now behaving normally, as symptoms of their disorder
• This highlighted major problems with the validity of diagnosis
• Cheniaux (2009) found poor inter-rater reliability between psychiatrists using DSM and ICD criteria to diagnose the same patients
• The classification systems may not be valid (concurrent validity) because psychiatrists diagnosed patients very differently when using each system
• Co-morbidity


  The occurrence of at least 1 other condition alongside schizophrenia
• Buckley et al (2009) found that around half of patients with a diagnosis of schizophrenia also have a diagnosis of depression (50%) or substance abuse (47%)
• Ellason & Ross (1995) found that people with dissociative identity disorder (DID) actually have more schizophrenic symptoms than people diagnosed as being schizophrenic
• Ketter (2005) points out that misdiagnosis due to symptom overlap can lead to years of delay in receiving relevant treatment
• Harrison et al's (1984) research suggested that those of West Indian origin were over-diagnosed with SZ, but white doctors in Bristol
• Cochrane (1977) also found increased incidence in diagnosis of people of Afro-Caribbean origin
• Longnecker et al (2010) found that since the 1980's men have been diagnosed with SZ more often than women
• Loring & Powell (1988) found that when patients were described as 'female' only 20% were given a diagnosis of SZ, compared to 56% when described as 'male' or no gender given
• Schizophrenia (SZ) is assumed to have a genetic influence
• Candidate genes for schizophrenia

  • PCM1
  • DTNBP1
  • RGS4
  • DISC1
  • NRG family of genes including NRG1
• Gottesman (1991) found that the rate of SZ is 13% if 1 parent has it, and 40% if both parents have it
• Gottesman and Shields found a concordance rate for SZ of 42% for MZ twins and 9% for DZ twins
• Tienari's adoption study found significantly more adopted children with SZ biological mothers developed SZ compared to a control group
• Ripke et al found 108 different gene combination variations associated with SZ
• Neural correlates


  Particular brain areas being correlated or associated with particular symptoms of SZ
• Dopamine Hypothesis


  SZ is linked to excess activity of dopamine in the subcortical areas of the brain (HYPERdopaminergia) associated with positive symptoms, and low activity of dopamine in the prefrontal cortex (HYPOdopaminergia) associated with negative symptoms
• Curran et al found that drugs which increase dopamine activity produce SZ-type symptoms, supporting the dopamine hypothesis
• Tauscher et al found that patients with SZ given antipsychotic drugs which lower dopamine levels had reduced occurrence of positive symptoms
• There are likely to be other neurotransmitters, such as serotonin and glutamate, involved in SZ, weakening the dopamine hypothesis as an incomplete explanation
• Patients with schizophrenia made more errors on an auditory task compared to the control group

  Auditory hallucinations are correlated with reduced activity in these brain areas