Schizophrenia Paper 3

• Schizophrenia


  A severe mental disorder characterised by a profound disruption of cognition and emotion
• Classification


  The process of organising symptoms into categories based on which symptoms cluster together in sufferers
• Classification systems used to diagnose schizophrenia

  • ICD 10 (published by the World Health Organisation)
  • DSM-V (published by the American Psychiatric Association)
• Positive symptoms of schizophrenia


  • Atypical symptoms experienced in addition to normal experiences
• Hallucinations


  Sensory experiences of stimuli that have either no basis in reality or are distorted perceptions of things that are there, usually auditory (hearing voices that other people can't hear)
• Delusions


  Bizarre/irrational beliefs that seem real to the person with schizophrenia, but they are not real, sometimes paranoid (persecutory) or grandiose
• Negative symptoms of schizophrenia

  • Those that appear to reflect a loss of or reduction in normal functions
• Speech Poverty (alogia)


  Lessening of speech fluency and productivity, patients may produce fewer words in a given time on a task of verbal fluency
• Avolition


  Reduction of interests and desires that are available to the individual, as well as an inability to initiate and persist in goal-directed behaviour
• Reliability


  The consistency of a classification system in assessing particular symptoms of schizophrenia
• Validity


  The extent to which a classification system accurately measures what it's supposed to measure
• Classification systems such as DSM-V are worthless unless they are reliable and valid
• Test-retest reliability of diagnosing schizophrenia has been reported as 37%, questioning the usefulness of classification and diagnosis
• Inter-rater reliability of diagnosing schizophrenia has improved over time, with studies reporting 54% agreement in the 1960s and 81% agreement in 2005 using DSM
• Studies have found inter-rater reliability correlations as low as 0.11 for diagnosing schizophrenia
• ICD and DSM do not always arrive at the same diagnosis for schizophrenia, indicating poor criterion validity
• Co-morbidity


  The extent that two or more conditions co-occur
• Schizophrenia is commonly diagnosed with other conditions like depression and substance abuse
• 25% of people with schizophrenia display significant OCD symptoms, with 12% fulfilling the diagnostic criteria, far greater than chance would suggest
• African Americans and British people of Afro-Caribbean origin are several times more likely than white people to be diagnosed with Schizophrenia, likely due to cultural bias rather than genetic vulnerability
• Psychiatrists may tend to over interpret symptoms and distrust the honesty of black people during diagnosis, leading to culture bias
• Before 1980 there were equal numbers of schizophrenia diagnoses for males and females, but since then, men are diagnosed far more than women, likely due to gender bias
• Females with schizophrenia are more likely to function better than men, which may bias practitioners to under diagnose schizophrenia in women
• There is considerable overlap between the symptoms of schizophrenia and other conditions like bipolar disorder and dissociative identity disorder, calling into question the validity of diagnosis
• Misdiagnosis due to symptom overlap can lead to years of delay in receiving treatment, during which time suffering and further degeneration can occur, as well as high levels of suicide
• Polygenic


  A product of the combined effect of a number of candidate genes
• 108 separate genetic variations were associated with the increased risk of schizophrenia
• Evidence for genetic susceptibility to schizophrenia


  • Family studies showing higher rates in biological relatives
  • Twin studies showing higher concordance in monozygotic twins
  • Adoption studies showing increased risk in adoptees with schizophrenic biological mothers
• Dopamine hypothesis


  Suggests an excess of the neurotransmitter dopamine in certain regions of the brain is associated with the positive symptoms of schizophrenia
• Schizophrenics are thought to have abnormally high numbers of D2 receptors on receiving neurons, resulting in more dopamine binding and therefore more neurons firing
• Drugs that increase dopamine, like amphetamines, can induce schizophrenic-like symptoms in 'normal' individuals
• Antipsychotic drugs that block dopamine activity in the brain can eliminate symptoms like hallucinations and delusions in schizophrenia
• Schizophrenics


  Have abnormally high numbers of D2 receptors on receiving neurons, resulting in more dopamine binding and therefore more neurons firing
• Revised dopamine hypothesis


  Positive symptoms caused by too much dopamine in subcortical areas (mesolimbic pathway), negative and cognitive symptoms caused by too little dopamine in prefrontal cortex (mesocortical pathway)
• Evidence for the dopamine hypothesis is inconclusive as stimulants affect many neurotransmitters, dopamine concentrations in post-mortem brain tissue have been negative or inconclusive, and other confounding factors like stress or smoking have rarely been considered
• There is strong evidence against both the original and revised dopamine hypotheses, as antipsychotics do not alleviate symptoms in about one-third of people, and hallucinations/delusions can be present even with normal dopamine levels
• Many people with schizophrenia, particularly those with negative symptoms, have enlarged ventricles (brain cavities filled with cerebrospinal fluid)
• Evidence on neural correlates cannot tell us anything about cause and effect
• There is overwhelming evidence for the role of biological factors in schizophrenia, but also evidence that environmental and psychological factors play a role
• Double bind


  An emotionally distressing dilemma in communication where an individual receives two or more conflicting messages, and one message negates the other