Schizophrenia, Biological Approach - AQA Psychology B

Heston

Aim

To investigate the role of genetics in schizophrenia

Method

Heston compared 47 adopted children whose biological mothers had schizophrenia to a control group that had no family history of schizophrenia

Results

none of the controls were diagnosed with schizophrenia but 16% of those whose biological mothers had schizophrenia were also diagnosed with it

Conclusion

inheritance does play a part

Evaluation

Findings were well above the 1% chance level, therefore inheritance can put people at risk of getting schizophrenia. However the percentage was still only 16% so there must be other factors such as several genes being respsible for schizophrenia or the environment that the child is raised in

Explanations

-Excess of dopamine can cause schizophrenia

-Dopamine is active in the Limbic system in the brain and governs emotion

Evidence

• Kimble - anti-psychotic drugs which reduce levels of Dopamine, also reduce symptoms of schizophrenia
• 
• Iverson - Schizophrenic patients show high levels of Dopamine in their brain

Evaluation

- does excess dopamine cause schizophrenia or does schizophrenia cause excess dopamine?

- receptors in the brain may be more sensitive in schizophrenics

Anti-Psychotic Drugs -

reduce positive symptoms

Chloropromazine -

blocks dopamie receptors in the brain, so neaurons do not respond to it

Side Effects -

- weigh gain, tremors, drowsiness, Tardive Dyskinesia

Evaluation -

- reduced number of long-stay patients in hospitals

- some patients do not find the side-effects difficult to cope with

- drug treatments are not a cure, symptoms can return if drugs are stopped

Monozygotic Twins -

have 100% of their genes in common

Dizygotic Twins -

has 50% of their genes in common (like normal siblings)

The biological approach would predict that where one twin has been diagnosed with schizophrenia, the concourdance rate would be higher for the MZ twins then the DZ

Gottesman and Shields -

-experiment proved that this was true

-MZ twins concourdance rate was 46%

-DZ twins concourdance rate was 14%

-46% (concourdance rate for MZ twins) suggests major contribution of genotype

-there is still a discourdance rate for DZ twins of about 40%. However studies have shown half of the discourdant group will go on to develop a schizoid

-low sample sizes

-Evidence from normal twin pairs (Lytton) suggest MZ twins grow up in a more similar environment then DZ twins. This could explain the concourdance rate partly.