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  • Created by: Katie
  • Created on: 10-03-11 22:35

Biological Explanations of Schizophrenia

Genetic Factors

  • Family studies: find individuals with SZ and determine whether their biological relatives are similarly effected. They have established that SZ is more common among biological relatives of a person with SZ and that the closer degree of genetic relatedness, the greater the risk.
  • Twin studies: offer a unique opportunity for psychologists to investigate relative contributions of genetic and environmental influences. If identical twins, who share 100% of their genes, are more concordant in terms of a trait like SZ than are fraternal twins who share only 50% of their genes, then this suggests that the greater similarity is due to genetic factors. Joseph (2004) found a concordance rate of 40.4% for identical twins, and 7.4% for fraternal twins – he based these results on studies prior 2001. More recent studies suggest a lower concordance rate. However, because the identical rate is much higher, researchers still argue that the findings support the genetic position.
  • Adoption studies: Used as there are difficulties when trying to differentiate genetic/environmental influences. Tienari et al., (2000) - in Finland, of the 164 adoptees whose biological mothers had been diagnosed with SZ; 11 also had SZ, comparing to just 4 of the 197 control adoptees (born to non-SZ mothers). Investigators concluded that the genetic liability to SZ had been 'decisively confirmed.' 

The Dopamine Hypothesis

- Dopamine: neurotransmitter that helps operate the brain. Dopamine Hypothesis states that messages from neurons that transmit dopamine fire too easily or too often, leading to the characteristics of SZ. The key role played by dopamine in SZ was highlighted in 3 sources of evidence:

  • Amphetamines - a drug which is a dopamine agonist, stimulating nerve cells containing dopamine causing the synapse to be flooded with this neurotransmitter. Large doses can cause the characteristic hallucinations and delusions.
  • Antipsychotic drugs - they block the activity of dopamine in the brain. By reducing stimulation of the dopamine system, these drugs eliminate symptoms such as hallucinations and delusions. The fact that these drugs alleviated many symptoms of SZ, strengthened the case for it being a contributory factor in SZ.
  • Parkinson's disease - low levels of dopamine activity are found in people who suffer from PD, a degenerative neurological disorder. It was found that people who were taking the drug L-dopa to raise their levels of dopamine were developing SZ type symptoms (Grilly, 2002).

- Problem for DH is that the drugs used to treat SZ by blocking


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