Genetic explanation of Schizophrenia

Question 1

What is the overview?

Answer 1

Chance of getting Sz for general population is 0.3-0.7%.
This increases if you are related to a schizophrenic.
Therefore it is genetically inherited.

Question 2

How does relation affect the chance of Sz? Examples?

Answer 2

Risk is increased as the degree of genetic relation increases.
Child - 13%
DZ twin - 17%
MZ twin - 48%

Question 3

What did Kendler et al. (1985) find?

Answer 3

Those with a 1st degree relative who suffers from Sz are 18x more likely to develop it too compared to general population.

Question 4

What does this genetic difference cause? x2

Answer 4

These genes result in critical neural pathways being disrupted and or damaged. The behavior controlled by these pathways are not carried out or don’t develop properly.
OR
It alters the functions of the brain e.g. sensitivity to certain chemicals.

Question 5

What did Harrison & Weinberger (2004)?

Answer 5

found that it may alter the functions of the synapse.

Question 6

What is synaptic pruning? How does it link?

Answer 6

Synaptic pruning is the shedding of weak or redundant connections between neurons in the brain as it matures. Those who carry genes which intensifies or accelerates this process are at higher risk of developing Sz.

Question 7

Supporting evidence?

Answer 7

+ Gottesman (1991): 17% concordance for DZ and 48% for MZ

+ Sherrington (1988): gene located on chromosome 5 has been linked to schziophrenia

Question 8

Conflicting evidence?

Answer 8

• Tamminga and Schulz (1991): suggest research has failed to identify a dominant or recessive gene which is responsible for Sz

Question 9

Other theories?

Answer 9

• neurotransmitters: says that dopamine is responsible
  + Can be used alongside neurotransmitters
• cognitive:

Question 10

Usefulness?

Answer 10

• concordance is not 100% so environment must play a role but it doesn’t account for this.
• reductionist: ignores cognitive explanation
• diathesis stress model: says we are genetically predisposed but environment triggers it - doesn’t account for this, says it’s all genetics
  + explains why there are trends of it in families. maybe test for it before - early intervention?
  + lots of research into it/evidence

Question 11

Testability?

Answer 11

• twin studies: environments aren’t completely the same between MZ which will account for the 52% missing concordance.