Biological Explanations

Question 1

Genetic Basis - Family Studies

Answer 1

1) Family studies find individuals who have SZ and determine whether their biological relatives are similarly affected more often than non-biological relatives.

RESEARCH SUPPORT:

2) Gottesman and Shield’s study, children with 2 schizophrenic parents had a concordance rate of 46%, children with one schizophrenic parent a rate of 13% and siblings (where a brother or sister had schizophrenia) a concordance rate of 9%.

Question 2

Twin & Adoption Studies

Answer 2

1) If monozygotic (MZ – genetically identical) twins are more concordant than dizygotic (DZ – who share only 50% of their genes) - This suggests that the greater similarity is due to genetic factors.

2) Adoption studies help separate genetic & environmental influences.

Question 3

Adoption Study - Tienari et al.

Answer 3

RESEARCH SUPPORT

1) In Finland of the 164 adoptees whose biological mothers with SZ, 6.7% also received a diagnosis of schizophrenia, compared to just 2% of the controls.

–> Findings showed a genetic liability to schizophrenia.

Question 4

Candidate Genes

Answer 4

1) Early research looked unsuccessfully for a single genetic variation to explain schizophrenia.

2) Schizophrenia is polygenic - requires several genes.

Question 5

Mutation

Answer 5

1) Schizophrenia can also have a genetic origin in the absence of a family history because of mutation in parental DNA.

Question 6

Neural Correlates - Dopamine

Answer 6

Role of Dopamine:

Dopamine (DA) is widely believed to be involved in SZ because it is featured in the functioning of brain systems related to the symptoms of schizophrenia.

Question 7

DA Hypothesis

Answer 7

1) Messages from neurons that transmit dopamine fire too easily or too often, leading to hallucinations and delusions that are the characteristic positive symptoms of schizophrenia.

2) Schizophrenics are thought to have abnormally high numbers of D2 receptors resulting in more dopamine binding and therefore more neurons firing.

3) Amphetamine is a dopamine agonist i.e. it stimulates nerve cells containing dopamine.

4) Antipsychotic drug block the activity of dopamine in the brain.

Question 8

Revised DA Hypothesis

Answer 8

1) The negative and cognitive symptoms of SZ are thought to arise from a deficit of dopamine in areas of the prefrontal cortex.

2) Evidence: neural imaging:

E.g. Patel et al (2010) used PET scans to assess dopamine levels in SZ and normal individuals and found lower levels of dopamine in prefrontal cortex of schizophrenic patients compared to their normal controls.

Question 9

Limitation of Explanation

Answer 9

ENVIRONMENTAL RISK FACTORS

1) Biological risk factors include birth complications and smoking THC-rich cannabis in teenage years.

2) Psychological risk factors include childhood trauma e.g. 67% with schizophrenia reported at least one
childhood trauma.

–> This means genes alone cannot provide a complete explanation for schizophrenia.