2. The genetic explanation of mental illness

Question 1

Genetic explanation (3)

Answer 1

• Each cell in the body contains 23 pairs of chromosomes. In each pair one is inherited
  from your mother and one from your father.
• The chromosomes in one pair contain the same genes but may contain different
  versions of the same gene called alleles. These are caused by random genetic mutations and some alleles are dominant where as others are recessive.
• This applies to medical conditions; if a child inherits one faulty allele then whether or
  not they get the medical condition will depend on several factors including:

    - What genes they inherit
    - Whether they’re dominant or recessive
    - Their environment

Question 2

Twin studies: Hilker et al (3 things)

Answer 2

• based on the Danish Twin Register and the Danish Psychiatric Research Register, they identified a sample of twins born 1951-2000 (N=31,524 twin pairs)
• Monozygotic twins - Share the same genes and the same environment and are genetically identical
  Found that if 1 MZ twin had sz then the concordance rate for the other was 33%
• Dizygotic twins - Share as many genes as siblings but share the same environment.
  Found that if 1 DZ had SZ then the concordance rate was 7%

Question 3

Hilker - Evaluation

Nature/Nurture?

Reductionist?

Useful?

Socially Sensitive?

Biological determinism?

Individualism?

Answer 3

Nature – this argument is linked to just nature – we inherit genes which cause schizophrenia from our parents

Nurture - concordance rates aren’t 100% so therefore can’t just be nature – more likely to be an interaction between the two – diathesis stress model suggests that we have a genetic vulnerability but that there is an environmental trigger that then causes the sz.

Reductionist – Focusing only on genetics is reductionist as it ignores other factors such as the environment.

Usefulness – Genetic counselling could be useful as it would advise people if they are at increased risk of Schizophrenia.

Socially sensitive – this could however lead to adults deciding not to have children, some governments may take this even further by introducing sterilization, higher medial insurance for those with higher risk of SZ

Biological determinism – this theory suggests that Schizophrenia is caused by our genetic make up. This is biological determinism, we have no control of our genetics

Individual explanation – Genes are different for individuals and they are within the person’s biology. This ignores situational factors

Question 4

Outline the role of Genes [5] (AO1) (model answer)

Answer 4

Schizophrenia is a psychotic disorder leading to a severe disruption in psychological thinking; characterized by a number of symptoms, hallucinations, delusions and negative behaviour being some examples.

Only 1% of the population are diagnosed with SZ, One explanation from the medical model that attempts to explain the likelihood of this is the genetic explanation. As we get 23 chromosomes from each of our parents this explanation looks at the likelihood of offspring developing this disorder.

This explanation also looks at twin studies to support it’s claims that SZ is in fact linked in someway to genetics. Gottesman family study showed the genetic influence on schizophrenia. The chance of a child developing schizophrenia or bipolar was 27.3 % if both parents had schizophrenia compared to 7 % in only one parent had schizophrenia. Similarly, if both parents had bipolar the chance of a child developing this disorder was 24.95% compared to 4.4%. Both these findings indicate that genes play a significant part in explaining where mental illness comes from.

Twin studies are also useful in supporting the role of genes because they share the same womb and moreover MZ twins share the same DNA. Hilker found that if one MZ twin had sz then the concordance rate for the other was 33%, in comparison to DZ twins the concordance rate was 7%. This suggests a genetic link for schizophrenia although this is clearly not 100% therefore environment may also play a role.