Caspi et al (2003)

Question 1

Where can the study be used? (4)

Answer 1

Research methods used in the biological approach.
To what extent does genetic inheritance influence behavior?
To what extent do biological factors influence abnormal behavior?
The etiology of one disorder.

Question 2

Aim

Answer 2

The aim of this study was to determine whether there is evidence for a gene-environment interaction (G x E) for a mutation of the serotonin transporter gene - 5-HTT

Question 3

5-HTT gene

Answer 3

The serotonin transporter is involved in the reuptake of serotonin in brain synapses

Question 4

Serotonin

Answer 4

Regulates mood - often called body’s natural “feel good” chemical

Question 5

Participants

Answer 5

Sample of 847 New Zealand 26-year-olds
* all members of a cohort that had been assessed for mental health on an every-other-year basis until they were 21
* divided into three groups based on 5-HTT alleles:
* group 1: two short alleles
* group 2: one short, one long allele
* group 3: two long alleles

Question 6

Method

Answer 6

Mutation of 5-HTT gene has shorter alleles: roughly 43% of people have it
* asked to fill in “Stressful life events” questionnaire - asked them about the frequency of 14 different events (financial, employment, health & relationship stressors - between 21 and 26)
* assessed for depression

Question 7

Results

Answer 7

• people who inherited one or more short versions of allele demonstrated more symptoms of depression and suicidal ideation in response to stressful life events
  
  • effect was stronger in those with three or more stressful life events
• simply inheriting gene was not enough to lead to depression but the genes’ interaction with stressful life events increased one’s likelihood of developing depression

Question 8

Limitations (4)

Answer 8

• Correlational studies do not establish a cause-and-effect relationship
• It is impossible to isolate variables and separate out social factors in twin studies
• Genetic arguments do not account for the variations in symptomology in different cultures
• It is not yet clear how genetic markers interact

Question 9

Strengths (3)

Answer 9

• Results have been replicated in different studies
• Modern research has allowed us to actually locate genetic variations using very large sample sizes
• Modern research recognizes the interaction of environmental and biological factors and does not use a solely reductionist approach