Bio explanation AO1

What are the three parts in the genetic basis of schizophrenia

1. Family studies

2. Candidate genes

3. Role of mutation

Explain family studies as a genetic basis of schizophrenia

Risk of schizophrenia increases in line with genetic similarity to relative with the disorder.

GOTTESMAN (1991)=> Large scale family study . 2000 pairs of twins

Aunt with schizophrenia => 2% chance of schizophrenia

Sibling with schizophrenia => 9%

Identical twin with schizophrenia => 48%.

Family members also share environment , but this correlation represents both genetic and environment

Explain candidate genes as a genetic basis of schizophrenia

RIPKE ET AL

Compared the genomes of 37000 patients, with 113000 controls .

108 genetic variations associated with increased risk of schizophrenia.

Schizophrenia is AETIOLOGICALLY HETEROGENEOUS (different combinations of factors can lead to condition).

It is also POLYGENIC (genes most likely coding for neurotransmitter- dopamine)

Explain the role of mutation as a genetic basis for schizophrenia

Mutation in parental DNA which can be caused by radiation, poison or viral infection.

BROWN ET AL

Evidence for mutation comes from positive correlation between paternal age and risk of schizophrenia (sperm mutation).

0.7% with fathers under 25

2% with fathers over 50.

Explain the dopamine hypothesis

Schizophrenia is the result of HIGH levels of dopamine in sub cortical areas of brain (HYPERDOPAMINERGIA).

Eg=>

excess dopamine receptors in pathways from sub cortex to Broca’s area => explains symptoms such as speech poverty or auditory hallucinations .

UPDATED => DAVIS ET AL

Proposed HYPODOPAMINERGIA ( low dopamine in brains cortex).

Low dopamine in prefrontal cortex could explain negative symptoms of schizophrenia.

It is thought that cortical hypodopaminergia leads to subcortical hyperdopaminergia.

Explain the neural correlates related to schizophrenia

Neural correlates are specific parts of the brain/ brain structure that are related to specific mental processes /behaviours..

NEGATIVE SYMPTOMS

Decreased levels of activity in VENTRAL STRIATUM linked to development of avolition.

POSITIVE SYMPTOMS

Decreased activity in the SUPERIOR TEMPORAL GYRUS + ANTERIOR CINGULATE GRYUS linked to development of auditory hallucinations.