Genetic explanation for schizophrenia Flashcards
How many genes are involved in schizophrenia?
Ripke reported 108 genetic variants that could mediate a vulnerability to the disorder - polygenic
What is the C4 gene?
The C4 gene is involved in immune function and synaptic pruning. Increased C4 activity is a genetic mutation ( it has survival value as it helps the brain to adapt and learn and prune synapses that are no longer needed) - but too much of this synaptic pruning can ‘backfire’. In adolescents , the human brain goes through synaptic pruning which is a good thing as this helps the brain prune ‘under used’ or ‘damaged’ synaptic connections to make space for new ones. C4 plays a role in pruning synapses BUT excessive pruning can lead to symptoms seen in SZ. This explains which SZ emerges after adolescence/early adulthood and not before. This also explains why the brains of Sz patients have a thinner cerebral cortex with fewer synapses compared to healthy brains.
Who conducted the family study?
Gottesman and Shields
What was found in the family study?
Children of two SZ parents have 46% chance of developing the disorder
MZ twins have 48% chance
DZ twins have 17% chance
First degree relatives have 6% chance
Second degree relatives have 5% chance
What was the adoption study?
Tienari et al (2000) completed an adoption study in Finland with over 164 adopted kids whose biological mothers had been diagnosed with schizophrenia. These were matched with kids whose biological mothers did not suffer from schizophrenia. The study found 11 of the sample whose biological mothers had schizophrenia had also been diagnosed with the condition compared to just 4 from the control group.
GENETIC EXPLANATION - Research evidence?
Joseph found that genetic similarity can increase the risk of developing the condition. He found a 40% concordance rate in SZ for MZ twins and a 7% concordance rate for DZ twins. This shows that genes have some influence on the development of the disorder, which adds credibility to the idea.
GENETIC EXPLANATION - Incomplete?
MZ twins do not have a concordance rate of 100%, which they should as they share the same genotype. Therefore environmental influences must have some influence - stress, alcohol, drugs and a difficult childhood. Therefore it has limited explanatory power.
GENETIC EXPLANATION - Methodological problems?
The explanation is biologically reductionist as it is simplified down to the genetic level of explanation. It is also biologically deterministic as it overlooks free will, which could be offensive.
GENETIC EXPLANATION - Scientific?
Genetics can be studied in a controlled, objective and falsifiable manner. We can gather quantifiable data by looking at the percentage similarity of genetic information between family relations. Therefore the conclusions are more trusted and more funding is likely to be given for further research.
