biological explanations of SZ

Question 1

What are the biological explanations of SZ?

Answer 1

Biological explanations of SZ are based on 2 factors, the genetic basis and neural correlates such as the dopamine hypothesis.

Question 2

Genetic basis of SZ

Answer 2

Genetic factors are tested through family, twin and adoption studies

family studies find people with SZ and see if their biological relatives are similarly effected more often than non biological relatives. They usually show the closer the genetic relatedness he greater the risk.

twin studies compare the difference between identical (MZ) twins and non identical (DZ) twins in terms of ZS concordance rates. So if it is genetic concordance rates should be higher for MZ twins. Looks at the nature v nurture debate.

Adoption studies try to separate nature and nurture, looks at MZ twins raised apart ort he adopted child of people with SZ.

Question 3

Candidate genes and SZ

Answer 3

There are specific genes associated with SZ however SZ is polygenic so it is effected by a combination of genes. A study of the genes of 37K SZ patients with 113k controls found that there are 108 separate gene combinations associated with an increased risk of SZ. The ones that were the most vulnerable are the ones connected to certain neurotransmitters like dopamine.

Question 4

Evaluation of genetic basis SZ

Answer 4

+) There is a lot of research support such as from Joseph’s twin study which found there as a 48% concordance rate for SZ between MZ twins while there was a 17% concordance rate for DZ twins. This shows that there is a higher chance that a child will have SZ if both their parents have SZ supporting the link between genes and SZ.

• ) However twin studies and family studies find it hard to separate nature and nurture, for example in twin studies MZ twins often wear the same clothes and are treated more similarly then DZ twins.
• ) SZ can also take place without family history, an explanation for this is that there could be mutation of the parents genes such as the sperm cell due to radiation infection etc. However this suggests that genetics is not the only factor effecting SZ.
• ) The diathesis stress model states that there is a genetic vulnerability in SZ but this vulnerability is only triggered if there was a stress trigger in someone’s life. This means even if you where born genetically vulnerable to SZ if you are not majorly stressed you will not develop SZ suggesting that other factors are involved.

Question 5

What are neural correlates?

Answer 5

Neural correlates are measurements of the structure or function of the brain that have a relationship with SZ especially different regions of the brain. Neurocorrelates also refers to how different neurotransmitters such as dopamine and serotonin at abnormal levels in different parts of the brain also effect SZ.

Question 6

Dopamine hypothesis

Answer 6

Neurotransmitters appear to work differently in people who have SZ, Dopamine (DA) seems to have an important role in SZ since is necessary in the functioning of several brain systems.

The dopamine hypothesis suggests that excess DA in certain regions of the brain are associated with the positive symptoms of SZ. Messages from neurons that transit dopamine fire to easily and often leading to hallucinations and delusions.

Question 7

two consequences of the dopamine hypothesis

Answer 7

Hyperdopaminergia in the subcortex- based on the original version of the hypothesis in explaining SZ, high levels of activity in an area of the brain such as the subcortex. An example is that higj amounts of dopamine in the Broca’s area could lead to speech issues or auditory hallucination.

Hypodopaminergia in the cortex- recent versions of the dopamine hypothesis have found lower levels of dopamine in the cortex, some suggest that low levels of DA in the prefrontal cortex leads to the negative symptoms of SZ.

Question 8

Strengths of the Dopamine hypothesis

Answer 8

• ) Neural correlates explanation is supported by drug research since dopamine agnostics which increase dopamine levels increase SZ symptoms if already p[resent and can induce mild versions of them in others. This supports the idea that high DA levels lead to SZ.
• ) A study found that the chemicals needed to produce DA are taken up faster in SZ patients compared to control populations. This suggests that SZ patients have higher DA levels as they produce more of it.

Question 9

weaknesses of the Dopamine hypothesis

Answer 9

• ) Other factors such as upbringing, genes and cognitive explanations could also explain SZ. Research has also found that another neurotransmitter glutamate is implicated in SZ. This suggests that DA is not the only factor effecting SZ.
• ) You can’t establish cause and effect as you don’t know if SZ causes abnormal dopamine levels or vice versa and we don’t know for sure if high or low levels of DA cause SZ.