A03 Biological Explanations For Schizophrenia

• Multiple sources of evidence for genetic susceptibility

  Very strong evidence for genetic vulnerability. Gottesman study shows how genetic similarity and shared risk of schizophrenia is related while Tienari presents children that even adopted into a family with no history of schizophrenia are at risk if biological parent has it. Studies conducted at molecular level show particular genetic variations which significantly increase risk of schizophrenia.
• Mixed evidence for the dopamine hypothesis

  Dompamine agonists like amphetamines increase levels of dopamine worsening schizophrenia and its symptoms yet anti-psychotic drugs reduced dopamine hypothesis. Both drugs suggest an important role for dopamine in the disease.
• Radioactive labelling (Mixed evidence for the dopamine hypothesis)


  Radioactive labelling studies like Lindstroem, found that chemicals needed to produced dopamine are take up faster in the brains of those with schizophrenia suggesting they produce more dopamine.
• Counter (Mixed evidence for the dopamine hypothesis)

  But Ripke et al study identified other neurotransmitters involved not just dopaine. Current research shifted to 'glutamate' neutrotransmitter for instance.
• The correlation-causation problem

  Alhough neural correlate studies are useful in flagging up particular brain systems that may work abnormally, there is an issue with causality and whether the unusual activity in a region causes the symptom. Thus the existance of neural correlates in schizophrenia tells us little.
• The role of mutation


  Schizophrenia can also have a genetic origin in the absence of a family history of the disorder. E.g: mutation in parental DNA which can be caused by radiation, poison or viral infection.

  Positive correlation between paternal age (risk of sperm mutation) and risk of schizophrenia, increasing from around 0.7% with fathers under 25 to over 2% in fathers over 50.
• The role of the psychologcial environment is important but unclear


  Evidence supports tole of biological factors in schizophrenia yet environmental factors like psychological ones during childhood play an important role. Genetics can only go so far, E.g: concordance rates are 50%.