Classification of Schizophrenia

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  • Classification of Schizophrenia
    • a diagnosis is made by a clinician through the use of a diagnostic manual, such as the DSM, or the ICD
    • a type of psychosis in which thoughts and emotions are impaired, causing a loss of external reality
    • affects around 1% of the population, commonly between 15 and 35yrs, although many live a normal life subsequently
    • Positive Symptoms
      • Hallucination - unreal physical perceptions
        • olfactory - scents
        • auditory - voices may be instructional, harmful, or narrative
        • visual - seeing lights, objects or faces
        • tactile - feeling physical sensations, eg bugs on the skin
      • Delusions - bizarre irrational beliefs
        • Delusions of Paranoia, often feeling they are at risk of harm
        • Delusions of Grandeur, experiencing inflated importance or talent
        • Delusions of reference, believing there are subliminal messages for them in the media
      • Disorganised Speech - results from abnormal thought processes
        • inability to organise thoughts is reflected i speech
        • rapid meaningless progression between topics (derailment)
        • may be so severe that no coherent meaning can be conveyed (word salad)
      • Catatonic behaviour
        • actions and movement may be grossly disorganised or catatonic in nature
        • includes inability to initiate or complete a task
        • results in difficulties in daily life and poor hygiene interests
        • reduced reaction to immediate environment, rigid postures or aimless motor activity
      • positive symptoms are in excess to normal funtion
    • Negative Symptoms
      • appear to be a reduction or absence of normal function
      • weaken the ability to cope with daily life but patients are unconcerned
      • having enduring (1yr) negative symptoms is the Deficit Syndrome, giving people a  worse prognosis
      • Speech Poverty - lessening of spoken productivity
        • thought to reflect slow or blacked thoughts
        • may produce fewer words in a given time, struggling to produce spontaneous language
        • less complex syntax
      • Avolition - a reduction in interests and desires
        • inability to initiate and persist in goal-orientated behaviour
        • reduction in self-initiated behaviours which are readily available to individual
      • Flat Affect - reduction in the range and intensity of emotion
        • includes facial expression, vocal tone, eye contact and body language
        • may show a deficit in prosody, and remove any indication of enthusiasm
      • Anhedonia - loss of interest and pleasure in activities
        • may be pervasive (all aspects of pleasure)
        • physical - lack of pleasure from food, bodily contact etc
        • social - lack of pleasure from interpersonal interactions
        • psychical anhedonia is a greater indicator of schizophrenia as it isn't comorbid with depression
    • Reliability
      • diagnostic reliability means that a classification must be repeatable
        • this may be reaching the same conclusion at different points in time (test-retest)
        • may be reaching the same diagnosis by two clinicians (inter-rater)
          • measured by the agreement kappa score
            • 0.7 shows strong reliability
            • schizophrenia classification is only 0.46
      • cultural differences
        • culture has a great influence on the diagnosis  process of schizophrenia
          • Copeland (1971) found when given the same desription 69% of US diagnosed, but only 2% of UK
        • cultural environments may affect the interpretation of the key characteristic (eg hearing voices)
          • african and indian ppts reported positive, helpful voices
          • US subjects all describes them as violent and hateful
    • validity
      • gender bias
        • affected by gender-based diagnostic criteria
        • affected by judgements of gender stereotypes
          • healthy behaviour may be equated with 'male' behaviour as the norm
          • more likely to perceive women as mentally unhealthy
      • symptom overlap
        • positive and negative symptoms are frequently found in other disorders
        • eg people with dissociative identity disorder display more schizophrenic symptoms
        • most people with schizophrenia have sufficient symptoms to also be diagnosed with another disorder
      • co-morbidity
        • important in the validity of mental illness diagnosis
        • refers to the extent to which two conditions can co-occur
        • eg substance abuse, anxiety, depression
        • Swets et al found OCD and schizophrenia are highly co-morbid (12%)
  • Evaluation
    • validity
      • gender bias - research support
        • 290 psychiatrists asked to read cases of patient behaviour
        • when patient was genderless or male, 56% diagnosed as schizophrenia
        • when described as female on 20% diagnosed the same patient with schizophrenia
        • but gender bias is less evident amongst female psychiatrists
      • consequence of co-morbidity
        • psychiatric and behavioural diagnoses accounted for 45% of co-morbidity
        • many patients with schizophrenia also had asthma, hypothyroidism
        • suggested that a psychiatric diagnosis can limit standard of overall medical care
      • difference in prognosis
        • no evidence that people with schizophrenia have any common outcomes
        • 20% tend to recover to previous level of functioning
        • 10% have lasting and significant improvement
        • 30% have improvement with intermittent relapse
        • suggests a diagnosis offers little predictive validity
    • reliability
      • lack of inter-rater reliability
        • little evidence that DSM is used reliably by clinicians
        • study has found kappa scores as low as 0.11
      • unreliable symptoms
        • it is only necessary that 'delusions are bizarre' for diagnosis
        • little inter-rater reliability (0.4) of what actually classifies as 'bizarre' however
        • suggests even central criteria lack reliability
      • cultural differences
        • study has established cultural and racial differences in diagnosis
        • prognosis for minority groups is often better
        • suggests patients experience less distress because of more supportive/ protective social support networks
        • called the ethnic culture hypothesis

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