Classification and diagnosis

• Schizophrenia is a mental disorder reportedly suffered by 1% of the world population and most commonly diagnosed between the ages of 15 and 35
• Schizophrenia can affect a sufferer's thought processes, physical functions and perception of reality
• Symptoms of schizophrenia can vary drastically between individual sufferers in terms of their type and severity
• Some sufferers may only encounter symptoms sporadically, whereas for others, these are more persistent
• Positive symptoms


  Symptoms in addition to normal functioning, including hallucinations and delusions
• Hallucinations


  Unusual perceptions of environment stimuli unique to the individual, which no one else can perceive
• Types of hallucinations


  • Auditory (e.g. hearing voices)
  • Visual (e.g. seeing lights or objects)
  • Olfactory (e.g. perceiving a disgusting smell)
  • Tactile (e.g. feeling something or someone is touching the skin)
• Delusions


  Irrational beliefs that seem real, but are not true in reality
• Types of delusions


  • Paranoid delusions (e.g. believing they are being persecuted by others)
  • Delusions of grandeur (e.g. believing they are famous or have superpowers)
• Negative symptoms


  Involve a reduction in normal functioning, including avolition and speech poverty
• Speech poverty


  A significant reduction in the amount or quality of what is spoken, including reduced verbal fluency and reduced language complexity
• Avolition


  The difficulty to begin and maintain goal-directed behaviour, involving significantly reduced self-motivation to take part in activities despite having the opportunity to do so
• Reliability refers to the consistency of measuring the symptoms of schizophrenia
• Test-retest reliability


  The extent to which a clinician makes the same diagnosis of schizophrenia on separate occasions from the same information provided by the patient
• Inter-rater reliability


  The extent to which different clinicians independently make the same diagnosis of schizophrenia for the same patient
• Culture bias


  Differential treatment towards ethnic groups, leading to over-diagnosis of schizophrenia in certain ethnic minorities
• Culture bias can affect the inter-rater reliability of diagnosis and classification because an individual reporting the same symptoms to clinicians from different cultural backgrounds may not receive the same diagnosis
• Evidence for culture bias affecting reliability of diagnosis

  • Luhrmann et al. (2015) found that Ghanaian and Indian participants diagnosed with schizophrenia reported positive experiences of hearing voices, whereas American participants reported negative experiences, which could lead to different diagnoses by clinicians from these cultures
• Symptom overlap


  When the characteristics of a particular disorder are shared with another, affecting the inter-rater reliability of diagnosis
• Evidence for symptom overlap affecting reliability of diagnosis

  • Ellason and Ross (1995) found that patients with dissociative identity disorder reported more positive symptoms than schizophrenic patients, leading to misdiagnosis of schizophrenia
• Symptom overlap can lead to misdiagnosis and consequently an incorrect therapy, with negative consequences
• Validity


  The accuracy of measuring symptoms and whether classification systems can distinguish schizophrenia from other disorders
• Concurrent validity


  The extent to which different classification systems identify symptoms of schizophrenia according to their criteria and arrive at the same diagnosis
• Predictive validity


  The extent to which a diagnosis of schizophrenia leads to a successful treatment in reducing a patient's symptoms
• Co-morbidity


  When a person has two or more disorders at the same time, affecting the validity of classification and diagnosis
• Evidence highlighting the issue of co-morbidity in diagnosis

  • Buckley et al. (2009) reported that 50% of schizophrenics had co-morbid depression, 47% substance abuse and 23% OCD
• Schizophrenics with co-morbid disorders are often excluded from research, leading to invalid findings
• Gender bias


  Differential treatment or representation of males and females, based on stereotypes, affecting the validity of diagnosis
• Evidence that gender bias affects the validity of diagnosis

  • Loring and Powell (1988) found that psychiatrists were more likely to diagnose schizophrenia in patients described as male compared to female
• Biological differences between the sexes may lead to under-diagnosis of females and reduce the validity of diagnosis