Biological Explantion For Schizophrenia - Gene

Question 1

Twin study

Answer 1

MZ - Mono-zygotic:
-twin born from 1 fertilised egg separated = 2 identical twins (share 100% of gene

DZ - Dizygotic
-twin born from 2 fertilised egg = 2 similar twin (share 50% of gene)

Concordance rate
-probability of certain conditions present in both twins if one has it
-Gottesman - MZ schizo concordance rate 48%, DZ 17%, 48% of other MZ has schizo if other has it

Question 2

Family study

Answer 2

Family members (parent + children) not just twins are compared on certain traits

Gottesman - closer genetic relatedness = increase risk of developing schizo (parent 6%, sibilings 9%, general population 1%)

Question 3

Adoption study

Answer 3

Help overcome issue of shared environment -
Parent + twins in same environment that causes schizo for person that has it

Tiernari et al - adoptees with biological schizo mother 6.7% diagnosed schizo
2% adoptee diagnosed with no schizophrenia mum
-shows effect of shared environment reduced gene does play part

Question 4

Schizophrenia is polygenic

Answer 4

O’Donovan et al - 108 locations in human genome link with schizophrenia. (83 not reported before). Sample = 80,000 + international. Some gene involved with brain issue and immune system involved with schizo.

-complement component 4, involve with synaptic pruning (removal of unnecessary neurone or synapse), process only happen naturally in teen

But actual cause still not discovered only areas involved

Question 5

Epigenetics

Answer 5

The gene for schizo must be triggered by environment, otherwise MZ twins have 100% concordance rate, but it’s 20-45%. Factors such as stress of pollutant from environment.

Question 6

Diathesis stress model

Answer 6

Combine gene + environment to explain schizophrenia

The schizo gene = diathesis, but only this will not cause illness
-only develop when environment trigger (stress) the gene for schizo (bad upbringing, brain injury)

-Genain quadruplets, dad is abusive but dad mother is schizophrenic

Question 7

Evaluation strength - Causal relationship

Answer 7

Interactionist approach
Diathesis - schizo gene does not cause schizo (at risk + carrier) (nature)
Stress - require environmental factors (upbringing or pollutant)

Question 8

Evaluation weakness - Research based on inheritability study

Answer 8

Twin + adopted children with schizophrenia are rare to find
-Gottesman 1% of population is schizo + 1.5% DZ, 0.5% MZ in uk
-> research hard to replicate so less research to compare = decrease reloability

Shared environment

Twins - may be treated similarly despite different personality or mistaken, some case copy sibling behaviour = lower validity
Family - similar environment as parent grew up or rough upbringing = lower validity

Question 9

Evaluation weakness - Reductionist

Answer 9

-although gene play a part in schizo there are other factors
>Rosenthal - 4 identical children schizo with grandmother schizo, but parent mentally unstable. Dad is abusive + Irritable and lack of interest in other = rough upbringing may cause schizo
-> nurture also played as a variable