bio explanations

• Genetic basis of schizophrenia:

  • There is a genetic component to schizophrenia 
  • Gottesman (1991)- family study - as genetic similarity increases, so does the probability of sharing schizophrenia 
• • Gottesman's study is a correlational study - as genetic similarity increases so does vulnerability to schizophrenia 
• Neural basis of schizophrenia:

  • The dopamine hypothesis- 

  Original hypothesis states that ……

  • Hyperdopaminergia In the subcortex - focused on high dopamine levels in central areas of the brain linked to excess dopamine receptors (more dopamine is binding so more neurons firing)
  • For example, an excess of dopamine receptors in pathways from the subcortex to Broca's area (speech production) may explain auditory hallucinations 
  • Hypodopaminergia in the frontal cortex there are lower levels of dopamine leading to negative symptoms such as speech poverty
• updated dopamine hypothesis....

  • Goldman (2004) identified low levels of dopamine in the prefrontal cortex (decision making and thinking) associated with negative symptoms of schizophrenia, resulting in cognitive problems 
  • It has also been suggested that cortical hypodopaminergia leads to subcortical hypodopaminergia (shows the updated hypothesis explains both high and low levels of dopamine)

   
• supporting evidence for neural explanation - Patel et al - used PET scans to assess dopamine levels in schizophrenia and non-schizophrenic individuals and found lower levels of dopamine in the dorsolateral prefrontal cortex - This supports the theory because it shows there is a link between dopamine levels in the brain and schizophrenic symptoms
• opposing evidence for neural explanation - Noli et al - against both of the dopamine hypotheses. Antipsychotic drugs do not relieve hallucinations or delusions in 1/3 of people. Symptoms can also be present in those with normal dopamine levels. this opposes the theory as it shows that dopamine may not be the only influence on schizophrenia, there may be other biological or environmental factors that have an influence
• supporting evidence for genetic explanation-   Tiernari et al – In Finland, 164 adopted children whose biological mothers were schizophrenic – 6.7% of adoptees received a diagnosis of schizophrenia. In a control group only 2% had schizophrenia. - This supports the theory because it shows that there is a genetic component involved in the development of schizophrenia
• opposing evidence for genetic explanation - Morkved et al – found that traumatic life events influenced schizophrenia – 67% of schizophrenics reported at least one childhood trauma - This opposes the theory because it shows other factors apart from genetics influence schizophrenia- the genetic explanation is not sufficient