Schizophrenia - biological explanations Flashcards
What are the 2 main biological explanations of schizophrenia
Genetic inheritance, neural correlates (hyperdopaminergia)
What is genetic inheritance primarily about
Function of C4 gene, twin studies, adoption studies
What is neural correlates (hyperdopaminergia) primarily about
Revised dopamine hypothesis, further neural correlates
How is schizophrenia genetically inherited
Genetic predisposition through faulty genes, C4 mainly which was discovered by Ripke et al. Mainly consist of biochemical imbalances or brain structure abnormalities
What is the function of the C4 gene
Found at synapses in CNS and mediates pruning. If fault, can lead hyper-pruning which leads to symptoms of schizophrenia
What does the understanding of the C4 gene causing SZ allow us to understand
Sufferers of SZ have thinner cerebral cortex’s with fewer synapses
According to Gottesman and Shields (1991) What are the chances of a child, (100% genetic similarity) of 2 SZ patients, to develop SZ
46%
According to Gottesman and Shields (1991) What are the chances of an identical twin, (100% genetic similarity) of which 1 has been diagnosed with SZ, to develop SZ
48%
According to Gottesman and Shields (1991) What are the chances of a first degree relative, (child) (50% genetic similarity) of 1 SZ patient, to develop SZ
13%
According to Gottesman and Shields (1991) What are the chances of a second degree relative, (grandchild) (25% genetic similarity) of 1 SZ patients, to develop SZ
5%
Why are twin/adoption studies used to investigate genetic inheritance
Isolate nature from nurture
What advantages do adoption studies have over twin studies
Can separate nature/nurture better as children are not raised by biological parents
What did MacDonald and Schultz (2009) find in their twin study
In MZ twins, if one is diagnosed with SZ, the other is 99x more likely to suffer from SZ
What did Tienari et al (2000) find in his adoption study
164+ adopted kids from Finland, whose mothers had SZ. Matched with kids whose mothers didn’t suffer from SZ. 7% oh those with SZ mothers had also been diagnosed with SZ, compared to 2% from other group.
What did Joseph (2004) find as supporting research of the biological explanations
40% concordance rate of SZ in MZ twins, 7% in DZ twins
What is a negative evaluation point for biological explanations
Don’t take into account environment - stress, alcohol, childhood etc, therefore an incomplete explanation
What are neural correlates
Where brain structure differences correlate with psychological disorders and symptoms e.g enlarged ventricles
What does the dopamine hypothesis state
Elevated levels of dopamine at post synaptic level are due to not enough being broken down during synaptic transmission, leaving too much in surrounding cells. Re - uptake processes may be impaired so too much dopamine in synapse. Presynaptic neurone release too much dopamine
What does the revised dopamine hypothesis state
No D2 receptors in pre frontal cortex despite dopamine deficiency in region, which is responsible for negative symptoms. This is known as HYPOdopaminergia
What did Randrup and Munkvad (1966) find as supporting research for neural correlates
Rats given dopamine amphetamines to increase levels 3 times per day for 6 days. Then showed lasting abnormalities such as attentional issues, a key symptom of SZ
What is a negative evaluation point for neural correlates
Incomplete explanation - antipsychotics to reduce and correct dopamine levels are 85% effective, so why not 100%? Must be other factors
What are further neural correlates
Brain structure and biochemistry
What are the forms of brain structure and biochemistry as further neural correlates
Enlarged ventricles - link to negative symptoms
Hypofrontality - Reduced activity in cortex of frontal lobes, negative symptoms
Hippocampus/amygdala - Decreased volume has been linked to negative symptoms
