Biological Explanation: Genes Flashcards
What is the relationship between schizophrenia and genes?
not a single gene involved: many, not sole cause, genes increase risk
What are the 2 models that link genes to schizophrenia?
liability threshold: more genes = more risk, some genes more risky. Diathesis-stress model = genes (diathesis) put at risk then stressors in environment trigger illness, determines who develops and when
What would you included in an AO1 description of genes and how they contribute to development?
Inherit 50% genes from each parent, genes build bodies: crucially brains, brain is source of mental states, schizophrenia is a disorder of mental states, schizophrenia may be heritable - genetic bases
How can the 2 genetic models of schizophrenia be combined?
higher liability threshold = more at risk so only need minor stressors to trigger illness, lower liability threshold = more serious stressors needed to trigger schizophrenia
What is the base rate for schizophrenia in the normal population?
> 0.5%
Who did a twin study meta analysis into genes and schizophrenia?
Gottesman 1991: 40 studies, pooled concordance for MZs 48%, DZs 17%, reared apart (14 cases) MZ = 58%
What is the issue with separated twin studies?
MZ twins shared womb and similar birth so concordance rate could be due to this, small sample
What are the more recent findings of twin studies into schizophrenia?
Cardno and Gottessman 2001: 5 newest studies, Europe and Japan, MZ = 41-65%, DZ = 0-28%, heritability = 80-85%
What can be said about the pattern of results from twin studies?
higher concordance rates for MZs than DZs but may be because they’re treated more similarly, not wholly genetic: MZ concordance would need to be nearer 100%, reasonable 5 gap between MZs and DZs
Who conducted an adoption study into foster home reared children?
Heston 1966: 47 adults with schizophrenic mothers and 50 controls, separated in 1st few days, 5/47 = 10% schizophrenic, none in controls
Who conducted a study into Finnish adopted children with schizophrenic mothers?
Tienari 1987: 7% chance of schizophrenia when mother schizophrenic only 1.5% in controls
What was the follow up study that Tienari conducted into adopted children with schizophrenic mothers?
2004: Finnish national sample, blind compare, adoptive rearing assessed, adoptees independently re diagnosed after 12 and 21 yrs, high risk adoptees = more sensitive to adverse rearing
What are the issues with Tienari’s studies?
mental health information of biological parents available to adopters so environmental factor: type of parenting and what children chosen, mainly Scandinavian
Who conducted a meta analysis into the association between dopamine D2 receptor gene and schizophrenia?
Glatt 2003: 24 studies, gene increased risk of schizophrenia by 30%, high significance: p=0.007
Who supports the Glatt finding in Asian populations?
Liu 2012: 16 studies, 4000 patients and controls, gene increased risk of schizophrenia by 40%
