Biological explanations of schizophrenia

• Gottesman - SZ is more common among biological relatives of a person with SZ than in the general population.
  • Greater the degree of genetic relatedness the greater the risk

If MZ twins are more similar in terms of SZ than DZ twins this suggests a strong genetic influcence.

• Joseph - concordance rate of just 40% for MZ  twins and just over 7% for DZ twins.

More recent studies have found lower concordance rates for MZ twins. 

Schizophrenics have abnormally high numbers of D2 dopamine receptors , resulting in dopamine neurons firing. 

May elad to problems of perception and thought found in SZ.

• PET and MRI scans - many schizophrenics have enlarged ventricles.
• Torrey - 15% bigger than normal

• Maladaptive traits would have been selcted out during the process of naturan selection - SZ would not exist. today.
• Stevens and Price - the presence of a charismatic leaders with SZ could have influenced members to follow and form a new group.
• 'group splitting hypothesis' argues that SZ is an extreme expression of an adaptive trait. 

• Greater concordance rates may be due to the way in which MZ twins are treated more similarly - 'identity confusion'

• Tienari - adoptees whose biological mothers had SZ, 6.7% of these individuals also developed the disorder. Compared to 2% of adoptees born to non schizophrenics
  • supports the genetic explanation

• Support is found by broadening the definition to include non psychotic 'schizophrenia spectrum disorder'. Rather than restricting it to full blown SZ. 

• Amphetamines - dopamine antagonists which stimulate nerve cells and cause the synapse to be flooded with dopamine. 
  • Large doses have caused hallucinations and delusions. 
• L-dopa is used to treat Parkinson's and raise dopamine levels
  • individuals have developed schizophrenic symptoms

• high levels of dopamine may be a consequence rather than a cause of SZ.
• Haracz - post mortem studies; those who showed elevated dopamine levels received AP drugs shortly before death.

• Enlarged ventricles may be an effect rather than the cause.
• Lyon - as the dose of AP drugs increased it led to enlarged ventricles.