Biological explanations of schizophrenia

From Gottesman’s results what can be concluded about SZ?

the risk of SZ increases as the amount of DNA you share with a relative increases

What are some of the concordance rates for identical twins, siblings and cousins?

• identical twins - 48%

• siblings - 9%

• cousins - 2%

What is a candidate gene?

a gene believed to be related to a particular trait

What does polygenic mean?

that schizophrenia is caused by a combination of different genes

How many genetic variations did Ripke et al find for SZ?

108

What does aetiologically heterogenous mean?

different combinations of genetic variations can lead to SZ in different people

How can someone have a genetic basis of SZ if no family members have it?

due to a mutation of parental DNA caused by radiation, poison or infections

Define neural correlates

patterns or structures of the brain that occur alongside an experience (i.e SZ) which are then perceived to be the cause of an experience

What is hyperdopaminergia?

hyper=too much. Refers to excessive amounts of dopamine

Where does hyperdopaminergia happen in SZ?

the subcortex

What is hypodopaminergia?

hypo = too little. Refers to a lack of dopamine

Where does hypodopaminergia happen in SZ?

in the cortex

What was the original dopamine hypothesis?

that SZ might be as a result of excessive levels of dopamine

E.g excessive dopamine in Broca’s area might lead to speech povery

Why was this concluded?

drugs that lower dopamine (antipsychotics) were found to reduce symptoms of SZ

What is the revised dopamine hypothesis?

it has also been found that some SZ sufferers experience abnormally low dopamine levels.

It might be localised:

• hyperdopaminergia in the sub-cortex

• hypodopaminergia in the cortex (causing cognitive deficits)

Why might one have abnormal levels of dopamine?

might be due to genetic variations or early experiences

How is the fact that the biological explanation of SZ is that is is biologically reductionist a weakness?

because by focusing only on biological factors, the explanation ignores key environmental influences such as childhood trauma, stress, and adverse life experiences. This means the biological explanation gives an overly narrow and incomplete account of schizophrenia. As a result, it may lead to limited or ineffective treatments

Give an example of this weakness

for example, dentical twins show only a 48% concordance rate for schizophrenia, even though they share 100% of their genes.

How is the fact that the neural explanation for SZ is also biologically reductionist as it overlooks the role of other neurotransmitters such as glutamate a weakness?

because it leads to a narrow and incomplete understanding of schizophrenia, which can limit treatment development. Treatments based solely on dopamine (e.g., antipsychotics) may not effectively target symptoms linked to glutamate, meaning some patients receive less effective care.

Give an example of this weakness

For example, McCutcheon et al. (2020) found raised glutamate levels in several brain regions of people with schizophrenia

How is the fact that the genetic explanation has strong evidence base a strength?

because it supports Gottesman’s graph about the chances of developing SZ as a result of their genetic make-up making the genetic explanation reliable

Give an example of this strength

for instance, it was found that biological children of parents with SZ are at a heightened risk of developing SZ, even when adopted into a different family. It was later found that there is a SZ concordance rate of 83% for MZ and 7% for DZ twins

How is the fact that the genetic explanation is biologically deterministic a weakness?

as saying that SZ has a strong genetic basis puts unnecessary blame on the parents and can lead to self-fulfilling prophecy

Give an example of this limitation

for example, when researchers such as Gottesman suggest that traits such as SZ have a genetic basis, these claims can influence how the parents of these individuals are perceived, potentially reinforcing stereotypes or justifying discrimination