schizophrenia

• schizophrenia

  • type of psychosis
  • disruption on cognition and emotion
  • contact with external reality and insight are impaired
  • affects 1% of the population
  • many sufferers end up homeless or hospitalised
• the 2 main classification systems:

  • ICD-11 - international classification of disease edition 11 by WHO
  • DSM-5 - diagnostic and statistical manual edition 5 by American psychiatric association
• what does the DSM-5 say about schizophrenia?

  • 2 positive symptoms of schizophrenia must be present for a diagnosis, only 1 if delusions are bizarre or hallucinations consists of 2 or more voices
  • disturbance must be continuous for 6 months
• what does the ICD-11 say about schizophrenia?

  • 2 or more negative symptoms sufficient for diagnosis or 1 positive symptom
  • recognises a range of subtypes of schizophrenia
• positive symptoms

  • atypical symptoms experienced in addition to normal experiences
  • hallucinations and delusions
• hallucinations

  • disturbances of perception in any of the senses
  • false perceptions that have no basis in reality or are distorted
• most common hallucination

  • auditory hallucinations
  • many schizophrenics report hearing voices or seeing people, telling them to do something or commenting on their behaviour
• delusions

  • firmly held irrational beliefs that have no basis in reality
• common types of delusions:

  • delusions of persecution - belief others want to harm, threaten or manipulate you e.g government, aliens
  • delusions of grandeur - the belief they are an important individual e.g they think they are jesus
  • delusions of control - the belief their body is under external control e.g controlled by aliens
  • delusions of reference - the belief that events in the environment appear to be directly related to them e.g personal messages communicated to them through TV
• negative symptoms

  • atypical experiences that represent the loss of a usual experience
  • avolition and speech poverty
• avolition

  • lack of purposeful, willed behaviour
  • difficulty or inability to start and continue with a goal directed behaviour
  • reduced motivation
  • e.g no longer interested in going out and seeing friends
• speech poverty

  • limited speech output with often repetitive content
  • often accompanied with a delay in sufferers verbal responses
  • not that they don't know the words but just have a difficulty in spontaneously producing them
• reliability in classification and diagnosis

  • consistency of diagnosis in classification system
  • inter-rater reliability - whether different clinicians using same classification systems give same patient the same diagnosis
  • test-retest - whether the same clinician using the same classification system with the same patient give the same diagnosis at 2 different time periods
• validity in diagnosis and classification

  • refers to accuracy
  • whether psychiatrists are giving an accurate diagnosis of schizophrenia
  • predictive validity - if diagnosis is valid it should lead to an effective treatment and we should be able to predict the prognosis of the disorder
  • descriptive validity - to be valid, patients with schizophrenia should differ in symptoms from patients with other disorders
• symptom overlap

  • considerable overlap between symptoms of schizophrenia and other conditions
  • e.g schizophrenia and bipolar disorder share positive symptoms
  • therefore questions validity of classification and diagnosis of schizophrenia
• co-morbidity

  • extent that 2 or more conditions occur together
  • common among schizophrenic patients
  • questions validity of classification and diagnosis of both illnesses
  • if many patients are diagnosed with both conditions, psychiatrists won't be able to tell the difference between the two conditions
• research evidence for symptom overlap and co-morbidity = Serper et al

  • strength
  • assessed patients with co-morbid schizophrenia and cocaine abuse, cocaine intoxication on its own and schizophrenia on its own
  • found that despite there being considerable symptom overlap in patients with schizophrenia and cocaine abuse, it was still possible to make an accurate diagnosis
  • suggests issue of symptom overlap is not as important as previously suggested
• research evidence for symptom overlap and comorbidity = ketter

  • weakness
  • misdiagnosis due to symptom overlap can lead to a major delay in receiving relevant treatment
  • can cause symptoms to become even worse
  • leads to severe consequences
  • focusing on fixing this issue can save money and lives
  • classification and diagnosis may lack validity
• research evidence for symptom overlap and comorbidity = buckley et al

  • weakness
  • half of those diagnosed with schizophrenia also have a diagnosis of depression or substance abuse
• cultural bias

  • significant variation between cultures when diagnosing schizophrenia
  • e.g African Americans and English people of Afro-Caribbean origin are several times more likely to be diagnosed with schizophrenia
  • But the rates in Africa and West Indies are not high so it can be said it’s due to cultural bias
  • Positive symptoms of hearing voices may be more accepted in African cultures due to cultural beliefs (communicating with ancestors)
• How does cultural bias affect validity of diagnosing schizophrenia?

  • psychiatrist could impose their own cultural standards about schizophrenia on others (imposed etic)
  • So biased towards what’s ‘normal’ in their culture (ethnocentric)
  • any deviation from what is considered normal in their culture could be misinterpreted and mislabeled as a symptom and so reduces validity
• How does cultural bias effect reliability in diagnosing schizophrenia?

  • there may not be agreement on diagnosis by psychiatrist across cultures
  • Suggests patient can display same symptoms but receive different diagnosis due to their ethnic background
• what are the long term implications of cultural bias in diagnosing schizophrenia?

  • labelling and stigmatisation
  • long term problems of getting/keeping a job
  • can lead to self fulfilling prophecy
• Research evidence for cultural bias - Copeland et al

  • limitations for reliability and validity - inter rater reliability
  • Gave description of patient to 134 US and 194 British psychiatrists
  • 69% of US psychiatrists diagnosed schizophrenia but only 2% of the British gave a diagnosis
  • Clinicians and researchers must pay more attention to effects of cultural differences on diagnosis
• research evidence for cultural bias - Escobar

  • white psychiatrists tend to over-interpret symptoms of black people
  • Factors like cultural difference in language and mannerisms, difficulty in relating between black patients and white therapists and myth that black people rarely suffer from affective disorders may cause the problem
  • Symptoms of ethnic minorities are misinterpreted
• gender bias in the diagnosis of schizophrenia

  • said to occur when accuracy of diagnosis is dependent on the gender of the individual
  • Due to gender biased diagnostic criteria or clinicians stereotypical beliefs held about that gender
• research evidence for gender bias - longenecker et al


  • found that since 1980s men have been diagnosed with schizophrenia more than women
  • Prior to this there had been no difference
  • Could be due to gender bias in diagnosis
  • womens better functioning (working and maintaining good family relationships) may bias practitioners to under diagnose despite men having similar symptoms
  • affects validity
• Research evidence for gender bias - Loring and Powell


  • randomly selected 290 male and female psychiatrists to read 2 case articles on patient behaviour
  • Asked to state their judgement on these individuals using standard diagnostic criteria
  • When patient describes as ‘male’ or no info given about their gender, 56% given diagnosis for schizophrenia
  • When patients described as ‘female’ only 20% given diagnosis
  • Questions validity - gender bias
  • Diagnosis influence not only by gender of patient but also the gender of the clinician
  • Questions reliability - inter rater reliability
• the 3 biological explanations:

  • genetics
  • dopamine hypothesis
  • neural correlates
• what does the genetic explanation say?

  • schizophrenia runs in families and is part genetic (inherited as genes)
• Gottesman and Shield - genetic explanation

  • large scale family study
  • investigated the concordance rate between monozygotic (MZ) twins and dizygotic (DZ) twins
  • found a higher concordance rate between MZ twins (48%) compared to DZ twins (17%)
  • because MZ twins are 100% genetically similar and DZ twins are 50% genetically similar
• why is schizophrenia polygenic - genetic explanation

  • different combinations of genes can lead to schizophrenia
  • 108 genetic variation leads to increased risk of condition
• Role of mutation - genetic explanation

  • brown et al
  • found positive correlation between paternal age and risk of schizophrenia increasing
  • older the father = higher risk of sperm mutation
• dopamine hypothesis - genetic explanation

  • neurotransmitters works different in the brain of an individual with someone with schizophrenia
  • dopamine has an excitatory effect associated with feeling of pleasure
  • unusual high levels of dopamine associated with positive symptoms of schizophrenia
  • abnormally high levels of D2 receptor sites --> more dopamine binds --> more neurones firing
• revised dopamine hypothesis - genetic explanation

  • davis and khan proposed the revised dopamine hypothesis
  • positive symptoms caused by higher levels of dopamine in subcortex
  • e.g excess levels of dopamine in Broca's area associated with auditory hallucinations
  • negative symptoms due to low levels of dopamine in prefrontal cortex e.g speech poverty
  • both high and low levels of dopamine involved in schizophrenia
• what is neural correlates?

  • measurements of the structure of the brain that occur in conjunction with symptoms of schizophrenia
• neural correlates of positive symptoms

  • lower activation levels in superior temporal gyrus and anterior cingulate gyrus found in those experiencing auditory hallucinations
• neural correlates of negative symptoms

  • ventral striatum involved in anticipation of reward
  • avolition involves loss of motivation
  • Juckel et al found moderate negative correlation between activity levels in ventral striatum and severity of overall negative symptoms
• AO3 - strength of genetic explanation - biological explanation

  • strong supporting evidence
  • Gottesman and Shield large scale family study
  • Tienari et al adoption study
  • found children with biological parents that suffer from schizophrenia still have a heightened risk of schizophrenia despite being adopted into a family with no history of schizophrenia
  • suggests genetic factors make some more vulnerable to the condition
  • but environmental factors also effect schizophrenia
  • but genetic susceptibility is more important
• AO3 - weakness of genetic explanation - biological explanation

  • assumes greater concordance for schizophrenia between MZ twins are due to genetic similarity rather than environmental similarity
  • MZ twins are treated more similarly because they are seen as 'one person' unlike DZ twins, who are seen as 2 distinct individuals
  • so MZ twins more likely to experience similar environments e.g same trauma
  • so difference in concordance rates may just be due to environmental differences