Schizophrenia - biological explanations

Question 1

Gottesman - twin study

Answer 1

• reviewed 40 twin studies
• concordance rates for MZ twins reared together was 48%, DZ twins was 17%
• suggests genetic influence as MZ twins have higher concordance rates

Question 2

Cardno and Gottesman - twin study

Answer 2

• concordance rates up to 65% for MZ twins and 28% for DZ twins
• hertiability estimates were around 85%

Question 3

Gottesman - separated twin study

Answer 3

• 58% concordance rates for MZ twins reared apart
• only used 14 twins
• environments and genetics separated so genes have role
• not 100% so indirectly supports diathesis-stress model
• genetic influence could be due to pre-natal environment

Question 4

Heston - adoption study

Answer 4

• 10% of participants separated from schizophrenic mothers were schizophrenic

Question 5

Tienari - adoption study

Answer 5

• adopted children who had schizophrenic mothers had 7% chance of developing schizophrenia
• risk for developing schizophrenia was 4 times greater in adopted children with schizophrenic mothers compared to adopted children from biological mothers without schizophrenia

Question 6

Wahlberg - adoption study

Answer 6

• re-examined the Tienari data and found strong effect of environmental factors where those at risk of developing schizophrenia were adopted into families with poor communication

Question 7

Glett - molecular genetics

Answer 7

• meta-analysis
• found associated between dopamine D2 receptor gene and schizophrenia
• no evidence of publication bias

Question 8

Liu - molecular genetics

Answer 8

• meta-analysis
• significant associations between D2 receptor and schizophrenia
• gene increased risk of schizophrenia by 40%

Question 9

Allen - molecular genetics

Answer 9

• across 118 meta-analyses

- total of 24 gene variants in 16 different genes showed significant effects on schizophrenia, increasing risk by 23%

Question 10

Howes and Kapur - dopamine hypothesis

Answer 10

• meta-analysis
• brain scanning studies
• high rates of presynaptic dopamine functioning in schizophrenia

Question 11

Howes - dopamine hypothesis

Answer 11

• meta-analysis of 44 studies
• compared schizophrenics to controls
• highly significant elevation in presynaptic dopamine function in schizophrenia with large effect size of 0.79