Biological Explanation - A03

Question 1

Research support

Answer 1

P) One strength of the genetic explanation is the strong evidence base.
E) Family studies such as Gottesman (facing page) show that risk increases with genetic similarity to a family member with schizophrenia. Adoption studies such as Pekka Tienari et al. (2004), show that biological children of parents with schizophrenia are at heightened risk even if they grow up in an adoptive family. A recent twin study by Rikke Hilker et al. (2018) showed a concordance rate of 33% for identical twins and 7% for non-identical twins.
L) This shows that some people are more vulnerable to schizophrenia as a result of their
genetic make-up.

Question 2

Environmental factors

Answer 2

P) One limitation of the genetic explanation is there is clear evidence to show that environmental factors also increase the risk of developing schizophrenia.
E) These environmental factors include both biological and psychological influences. Biological risk factors include birth complications (Morgan et al. 2017) and smoking THC-rich cannabis in teenage years (Di Forti et al. 2015).
E) Psychological risk factors include childhood trauma which leaves people more vulnerable to adult mental health problems in general but there is now evidence for a particular link with schizophrenia. In one study by Nina Morkved et al. (2017), 67% of people with schizophrenia and related psychotic disorders reported at least one childhood trauma as opposed to 38% of a matched group with non-psychotic mental health issues.
L) This means that genetic factors alone cannot provide a complete explanation for schizophrenia.

Question 3

Evidence for dopamine

Answer 3

P)One strength is support for the idea that dopamine (DA) is involved in schizophrenia.
E) First, amphetamines increase DA and worsen symptoms in people with schizophrenia and induce symptoms in people without (Curran et al. 2004).
E) Second, antipsychotic drugs reduce DA activity and also reduce the intensity of symptoms (Tauscher et al. 2014). Third, some candidate genes act on the production of DA or DA receptors.
L) This strongly suggests that dopamine is involved in the symptoms of schizophrenia.

Question 4

Glutamate

Answer 4

P) One limitation of the dopamine hypothesis is evidence for a central role of glutamate.
E) Post-mortem and live scanning studies have consistently found raised levels of the neurotransmitter glutamate in several brain regions of people with schizophrenia (McCutcheon et al. 2020).
E) In addition, several candidate genes for schizophrenia are believed to be involved in glutamate production or processing.
L) This means that an equally strong case can be made for a role for other neurotransmitters.