schizophrenia

• Schizophrenia


  A psychotic disorder marked by severely impaired thinking, emotions, and behaviours. Schizophrenic patients are typically unable to filter sensory stimuli and may have enhanced perceptions of sounds, colours, and other features of their environment
• Symptoms of schizophrenia


  • Positive symptoms
  • Negative symptoms
• Positive symptoms


  Enhance the typical experience of sufferers, and occur in addition to their normal experiences e.g. hallucinations and delusions
• Negative symptoms


  Take away from the typical experience of sufferers, and so represents a 'loss' of experience e.g. speech poverty and avolition
• Hallucinations


  A positive symptom of schizophrenia, which is characterised by a distorted view/perception of real stimuli or perceptions of stimuli which have no basis in reality
• Delusions


  A positive symptom of schizophrenia and are a set of beliefs with no basis in reality at all
• Speech poverty


  A negative symptom of schizophrenia which occurs when there is an abnormally low level of the frequency and quality of speech
• Avolition


  A subjective reduction in interests, desires and goals and a behavioural reduction of self-initiated and purposeful acts, including motivational deficits
• Classification systems for mental disorders

  • Diagnostic and Statistical Manual (DSM-V)
  • International Classification of Disease (ICD-10)
• Differences between DSM and ICD

  DSM has more specific diagnostic criteria and requires at least 2 or more of delusions, hallucinations, disorganized speech and catatonic behaviour, whereas the ICD-10 takes a broader approach to diagnosis
• Subtypes of schizophrenia


  • Positive schizophrenia
  • Mixed schizophrenia
• There is a significant co-morbidity (high frequency of diagnosis of two disorders together) between schizophrenia and other mental health disorders, such as OCD and post-traumatic stress disorder
• There may be gender bias in the diagnosis of schizophrenia, as suggested by Longenecker et al (2010)
• There is also a problem of racial bias in the diagnosis of schizophrenia, as suggested by Escobar et al (2012)
• Genetic basis of schizophrenia

  Schizophrenia runs in families, and so appears to have a genetic basis. Gottesman (1991) demonstrated a positive correlation between the increasing genetic similarity of family members and their increased risk of developing schizophrenia
• Genetic basis of schizophrenia

  • Monozygotic twins (48% concordance rate)
  • Dizygotic twins (17% concordance rate)
  • Siblings (9% concordance rate)
  • Parents (6% concordance rate)
• Candidate genes for schizophrenia

  Genetic variations which marginally increase the risk of developing schizophrenia. Schizophrenia is a polygenic disorder i.e. has multiple, contributing candidate genes
• Dopamine hypothesis


  The original dopamine hypothesis suggests that hyperdopaminergia (abnormally high dopamine levels) in the subcortex is responsible for schizophrenia, whereas the revised dopamine hypothesis suggests that hypodopaminergeria (abnormally low dopamine levels) in the cortex is more likely to be responsible

  
• Hyperdopaminergia in Broca's area

  May be responsible for the positive symptom of auditory hallucinations
• Hypodopaminergia in the prefrontal cortex

  May be responsible for negative symptoms of schizophrenia, such as speech poverty and avolition
• Neural correlates


  Specific patterns of cortical activity or neural structures which coincide with specific psychological symptoms, and so are assumed to contribute towards those symptoms
• Abnormally low levels of activation in the ventral striatum


  May be associated with the negative symptom of avolition
• Mis-identification of self-generated speech in patients with auditory verbal hallucinations

  Associated with functional abnormalities in the anterior cingulate and left temporal cortex
• The risk of having offspring with schizophrenia increased by over 1.3% if the father was over 50 years old, compared to if the father was under the age of 25
• The evidence for the dopamine hypothesis can be best described as 'mixed'
• Antipsychotics


  Act as dopamine antagonists and so reduce dopamine activity by binding to complementary receptors on the post-synaptic membrane
• Antipsychotics alleviated the symptoms of schizophrenia, suggesting that dopamine has a key role in its development, in line with the predictions of the dopamine hypothesis
• Some researchers have criticised the dopamine hypothesis and biological explanations of schizophrenia as emphasising the role of dopamine too far
• The neurotransmitters glutamate and serotonin may also play a key role in schizophrenia, as evidenced by the antipsychotic Clozapine acting upon both of these substances and being more effective than other atypical antipsychotics in reducing schizophrenia symptoms
• Neural correlates as a means of explaining schizophrenia

  • Correlational evidence does not take into account the 'third variable problem', whereby a third unstudied factor could be affecting both outcomes
  • Correlational research cannot be used to reliably demonstrate a 'cause and effect' relationship between two variables
• Psychological explanations for schizophrenia

  Suggest that the development of schizophrenia is due to abnormal family communication styles, mixed messages, and the stress caused by high levels of expressed emotion
• Schizophrenogenic mother


  Characterised as being cold and rejecting, leading to a tense family climate lacking in honesty, which develops paranoia and anxiety in the child
• Double-bind theory


  Within a family, the child receives mixed messages from both parents about what is right or wrong, leading to the child seeing the world as unfair and confusing
• Expressed emotion


  The level and type of emotion shown towards the patient by their carer, which is often a significant source of stress for the patient
• Dysfunctional thought processes


  Abnormally-functioning thought processes which lead to unpleasant/undesirable outcomes, including metarepresentation and central control
• Metarepresentation


  The cognitive ability to differentiate between our own actions and the actions of others, allowing us insight into the intentions and emotions of others, as well as maintaining a realistic/functional view of our own goals and intentions
• Central control


  The cognitive ability to carry out a deliberate action whilst suppressing an automatic response
• Dysfunctional thought processes are implicated in the development of schizophrenia, and faulty central control skills may be responsible for some schizophrenia symptoms
• Psychological explanations for schizophrenia do not accommodate for biological factors, and place an increasing amount of blame on the families and caregivers of patients
• Antipsychotics


  Dopamine antagonists that bind to complementary dopamine receptors on the postsynaptic membrane, preventing dopamine molecules from binding and reducing neurotransmission to a normal level