Biological Explanations For Sz

Question 1

What is the genetic inheritance for sz
What did RIPKE say

Answer 1

Some may have a genetic predisposition to sz - condition partly inherited = disorder runs in family through faulty genes.
Several genes are involved (polygenic)
RIPKE - 108 genetic variants could mediate vulnerability to disorder ( variations on chromosomes 8 and 11, and C4 gene)
= having some faulty genes ^ vulnerability to dev sz by inheriting biochemical imbalances.

Question 2

What did Gottesman and Shields say abt genetic inheritance for sz

Answer 2

Children of 2 sz pts share 100% genetic similarity + 46% chances of developing disorder
MZ twins (identical) share 100% genetic similarity and have 48% chances of dev sz if one twin had been diagnosed.
children of first degree relatives share 50% genetic similarity + 13% chance of dev sz if parent has been diagnosed.
Second degree - share 25% similarity + 5% chance dev of nan got diagnosed.

Question 3

What did TIENARI say

Answer 3

Adoption study
164 kids biological mothers had sz matched with kids mothers didn’t have sz.
Found 11 (7%) bio mothers had sz were also diagnosed with sz compared to just 4 (2%) from control group
= helps validate idea that sz had genetic component - adopted kids don’t share environmental influences with bio mothers + provides CONCURRENT VALIDITY for role of genes in sz.

Question 4

EV positive for genetic inheritance for sz

Answer 4

Evidence - JOSEPH 40% conc rate for MZ (share 100% gen sim) and 7% concordance rate for DZ twins sharing 50% genetic similarity.
Higher conc rate for MZ when environmental influences assumed to be no more similar than DZ
= genes has influence on dev of sz

Knowledge of genetics + SZ has useful practical applications - can have significant impact on family planning. Idvs with sz made aware of risks in their children developing sz - think about alternative options (adoption) - advised by clinicians on their own risks of dev sz
= biological approach + understanding cause has had tangible effects in society.

Question 5

EV negative genetic inheritance sz

Answer 5

Family studies into SZ have methodological issues - kids may pick up on deviant behaviour - imitating key role models (flat effect) or pick up deviant parenting styles based on how they were raised (internal working model)
= genetic evidence used to validate the role of the environment in sz

Genetic expl incomplete - genetics can’t be sole cause for sz - MZ twins would have a concordance rate of 100% and not 40% = nurturing (env) influences must play a role in dev (stress, drugs, childhood)
= biological approach of sz has limited explanatory power + more holistic approach to understanding sz

Question 6

Explain dopamine hypothesis for sz
And DAVIS

Answer 6

HYPERDOPAMINERGIA
Sz caused by elevated levels of dopamine at key synaptic sites wwith in subcortical region of the brain (Mesolimbic + limbic pathways)
Excess DA = system overload (too many imply less being transmitted) = positive symptoms (delusions)
Caused by factors (presynaptic neurones releasing too much DA

= abnormalities in DA can manifest in odd behavioural patterns found in some sz patients (hallucinations)

Davis - prefrontal cortex there are no D2 receptors - deficiency of DA in this region. Davis suggested low levels of DA in this region (mesocortical pathway) and responsible for negative symptoms (avolition) HYPO DOPAMINERGIA

Question 7

Ev positive dopamine explanations sz

Answer 7

Evidence - RANDRUP + MUNKVAD created sz like behav sample of rats giving them da agonists (amphetamines) raising levels x3 a day for 6 days
Rats showed long lasting abnormalities (unable to filter out irrelevant sounds)
Reversed with AP medication.
= link between high levels of DA and sz - supports hyperdopaminergia

Practical applications - understanding sz is linked with high levels of da in limbic and mesolimbic pathways allowed clinicians to prescribe APs - block activity of da and have shown to be effective in up to 85% pts with sz.
= neural expl for understanding cause of sz has tangible effects in society.

Question 8

EV negative dopamine expl sz

Answer 8

Correlational data - clearly a relationship between high da and sz but can’t infer cause and effect - did high da cause sz or did sz cause high da - third unknown factor causes both (poor communication in household)
= da hypothesis for sz is merely correlational + limited use

Dopamine expl is incomplete - most pts of sz are prescribed APs to reduce DA - been effective up to 85% pts with sz —> why da levels don’t decrease for the remainder 15% - must be other factors beyond da involved in the development of sz
= limited explanatory power.