Diagonsis and classification

• Classification of mental disorder

  The process of organising symptoms into categories based on which symptoms frequently cluster together
• Schizophrenia

  A severe mental disorder where contact with reality and insight are impaired, and example of psychosis
• Positive symptoms of schizophrenia

  • Hallucinations
  • Delusions
• Hallucinations

  Positive symptom of schizophrenia. They are sensory experiences that have either no basis in reality or are distorted perceptions of things that are there. For example hearing voices or seeing people who aren't there.
• Delusions

  Positive symptom. They involve beliefs that have no basis in reality e.g., a person believes that they are someone else or that they are the victim of a conspiracy e.g. delusions of grandeur
• Negative symptoms of schizophrenia

  • Speech poverty
  • Avolition
• Speech poverty

  Negative symptom of schizophrenia. It involves reduced frequency and quality of speech. It may include a delay in verbal responses during coversation.
• Avolition

  A negative symptom of schizophrenia. It involves the loss of motivation to carry out everyday tasks (e.g. work, hobbies and personal care) and results in lowered activity levels and unwillingness to carry out goal-direction behaviours
• Co-morbidity

  The occurrence of two disorders/conditions together e.g., a person has both schizophrenia and a personality disorder. When two conditions are frequently diagnosed together it calls into question the validity of classifying the two disorders separately - confuses diagnoses and treatment.
• Symptom overlap

  Occurs when two or more conditions share symptoms. Where conditions share symptoms this calls into question the validity of classifying the 2 disorders separately
• Diagnosis and classification are interlinked. In order to diagnose a specific disorder we need to distinguish one disorder from another. This is done by identifying clusters of symptoms that occur together and classifying this as one disorder. Diagnosis is then possible by identifying symptoms and deciding what disorder a person has
• Schizophrenia is a collection of seemingly unrelated symptoms. There are many misconceptions and exaggerations surrounding the nature of schizophrenia
• Systems for classification of mental disorder

  • World Health Organisation's International Classification of Disease (ICD-10 version 11 has been used since 2022)
  • American Psychiatric Association's Diagnostic and Statistical Manual edition 5 (DSM-5)
• These systems (ICD-10 and DSM-5) differ slightly in their classification of schizophrenia, in DSM-5 one positive symptom must be present where as 2 or more negative symptoms must be present for a diagnosis under ICD-10
• Reliability


  The extent to which the diagnosis of schizophrenia is consistent - inter-rater and test-retest
• Validity 


  The extent to which the diagnosis and classification techniques measure what they are designed to measure i.e. schizophrenia
• One limitation of diagnosis of schizophrenia is co-morbidity

  -Co-morbidity is when 2 or more conditions occur together. If they occur together a lot it calls into question whether they are acctually a single condition -Buckley (2009) - 50% with schizophrenia also had depression, 47% substance abuse, 23% OCD

  -Issue because suggests schizophrenia is not one single condition, or could be that other conditions cause schizophrenia (substance abuse), classification inaccurate

  -schizophrenia commonly diagnosed with other conditions (co-morbidity)
• One limitation of a diagnosis of schizophrenia is low reliability


  Cheniaux et al (2009) had 2 psychiatrists independently diagnose 100 patients using both DSM and ICD criteria. Inter-rater reliability was poor. One psychiatrist diagnosed 26 with schizophrenia using the DSM and 44 using ICD. 2nd psychiatrist diagnosed 13 with DSM and 24 with ICD. This inconsistency between mental health professionals and the different classification systems is a limitation in the diagnosis.
• An additional limitation in the diagnosis of schizophrenia is validity


  A standard way to asses the validity of diagnosis is criterion validity - do difference assessment systems arrive at the same diagnosis for the same patient? Cheniaux et al's study shows that schizophrenia is much more likely to be diagnosed using ICD than DSM. This suggests that schizophrenia is either over-diagnosed in ICD or under-diagnosed in DSM. This is poor validity and a weakness of the diagnosis.
• Another limitation is gender bias in the diagnosis of schizophrenia

  Longenecker et al (2010) reviewed studies of the prevalence of schizophrenia and concluded than since the 1980s men have been more often diagnosed than women. Cotton et al (2009) found female patients typically function better than men. This may explain why some women escape diagnosis because their better interpersonal functioning may bias practioners to under-diagnose schizophrenia. This is a problem because women and men with similar symptoms may experience differing diagnoses.