SZ - genetic explanation

Question 1

genes as an explanation of schizophrenia

Answer 1

Genetic inheritance suggests that SZ is a heritable condition meaning it passes down from one generation to the next.

Question 2

How many genes are linked to schizophrenia?

Answer 2

700+ genes linked to SZ

Question 3

Which generic variations cause schizophrenia?

Answer 3

★ COMT gene provides instructions for enzymes which break down dopamine

• Variations with COMT leads to poor regulation of dopamine (excess) in prefrontal cortex

★ DISC 1 gene is responsible for the creation of GABA which regulates dopamine and glutamate in the limbic system

• Variations with DISC 1 means you are 1.4 times more likely to develop SZ because of irregular neurotransmitter activity

Question 4

Diathesis-stress model

Answer 4

• Inheriting a genetic variation (COMT/DISC 1) makes an individual more vulnerable/predisposed to developing SZ rather than the genetic variation directly causing SZ
• SZ symptoms are triggered by environmental factors (trauma, stressful life events, drug use etc.)

Supported by Gottesman & Shield

Question 5

state the aim of gottesman and shield’s study

Answer 5

Investigate whether SZ had a genetic basis by comparing the concordancerate of SZ in MZ and DZ twins

Question 6

Describe the procedure of gottesman and shield

Answer 6

● Looked at patient records from psychiatric hospital over a 16 year history (1948-1964)

● 62 patients were identified, their twins were tracked down to participate

● Zygosity was determined using fingerprint testing, blood testing and resemblance testing

● Primary data collected: questionnaires and interviews with twins and parents, tape recordings of verbal behaviour from semi-structured interviews, personality tests and tests to measure disordered thinking

● Secondary data: Hospital notes from admission to psychiatric ward

Question 7

Findings of gottesman and shield

Answer 7

There was a significant difference between MZ and DZ twins

Severe SZ - (MZ - 75%) (DZ - 22%)
Mild SZ - (MZ - 17%) (DZ - 0%)

Question 8

Conclusions of gottesman and shields

Answer 8

• The closer the genetic relationship, the greater the likelihood that if one was diagnosed with SZ, the other twin will also develop it
• However MZ twins did not have 100% concordance, implying that SZ is not caused entirely by genes, instead genes predispose someone to SZ making them more vulnerable to SZ by lowering their ability to cope with stress and trauma, so when they experience these factors through the environment this triggers the onset of SZ
• The diathesis-stress model considers the interaction between biological and environmental factors

Question 9

Genetic exp. SZ - supporting evidence

Answer 9

P - Supporting evidence

E -Gottesman and Shields studied twins and found that SZ is heritable. There was a significant difference in concordance for severe SZ in twins-
MZ - 75% DZ- 22%
The closer the genetic relationship, the greater the likelihood that if one twin was diagnosed with SZ, the other twin will also develop it

T = valid

Question 10

Genetic exp. SZ - contradicting evidence

Answer 10

P - Contradicting evidence - concordance rates are never 100%

E - Gottesman and Shields found that MZ twins did not have 100% concordance. This implies SZ is not entirely caused by genes, instead genes made predispose to SZ. More vulnerable to SZ by reducing ability to cope with environmental risk factors (stress,trauma) which triggers SZ

T = less valid

Question 11

Genetic exp. SZ - evidence has high scientific status

Answer 11

P- Evidence uses controlled lab cond. + objective measurements

E - Dahoun reviewed 14 studies. Concluded that DISC 1 is associated with dopa dysregulation

E - Egan proposed a link between decreased dopamine activity in prefrontal cortex and COMT gene which increases risk of SZ by 50%
Shows how genetic variations underpin neurotransmitter activity vulnerable to SZ

T = high scientific status

Question 12

Genetic exp. SZ - can’t explain all aspects of SZ

evaluation

Answer 12

P: can’t explain all aspects of SZ

E - The MZ twins in Gottesman and Shield’s study are more likely to be treated more similarly due to more similar appearance and because they are always the same sex, whereas DZ twins can be different sexes, so concordance rate may be as much due to shared environment as shared genes

T - less valid, not a full explanation

Question 13

Genetic exp. SZ - application (treatment)

Answer 13

genetic counselling is used as a treatment
when patient receives diagnosis of SZ, ‘recurrence risk’ can be calculated, which is the likelihood SZ will reoccur in offspring

counsellor helps
* families to understand recurrence risk
* reduces fear of the inevitability of SZ
* people to make rational choices about family planning

T - useful to society

Question 14

Genetic exp. SZ - treatments dont work for all

Answer 14

P: treatments don’t work for all

E: research suggests up to six different genes may be involved. variations of these genes exist within individuals. this means it is hard to identify specific genes

predictions about ‘recurrency risk’ (the likelihood of another family member developing it) should be treated with caution

T = limited usefulness

Question 15

Genetic exp. SZ - focus on nature side of debate

Answer 15

P: focus on nature side of debate

E: tienari found that adopted children from families with SZ had more chance of developing it (9.4% lifetime risk) than adopted children from families with no history of SZ (1.2% lifetime risk)

T = detailed, scientific evidence

Question 16

Genetic exp. SZ - reductionist, ignores nurture

Answer 16

P: reductionist, ignores nurture

tienari shows the interaction between nature and nurture
adopted children from families with SZ were less likely to develop the illness if placed in a ‘good’ family with kind relationships, empathy, security, etc.
so environment does play a part in triggering the illness if predisposed to it (diathesis stress model)

T = reduces validity