Caspi Et Al Study (bio)

Question 1

Caspi Et Al Study (bio)

Aim

Answer 1

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 2

Caspi Et Al Study (bio)

Procedure

Answer 2

• Approx 850 New Zealand 26-year-olds (members of a cohort that had been assessed for mental health on an every-other-year basis from the Dunedin Study)
• Divided into three groups based on their 5-HTT alleles:
  
  • Group 1: two short alleles (ss)
  • Group 2: one short and one long allele (sl)
  • Group 3: two long alleles (ll)
• Completed a “Stressful life events” questionnaire which asked them about of 14 different events between ages of 21 and 26
  
  • The 14 different life stressors: Employment, Housing, Relationship, Financial, Health, Holmes-Rahe Life Stress Inventory
• Assessed for depressive symptoms and episodes in the past year
• “Someone who knows them well” also completed a survey about them

Question 3

Caspi Et Al Study (bio)

Findings

Answer 3

• Participants with two short alleles had a greater risk of depression (in the past year) after four or more stressful events over a period of five years
• Participant with two long alleles and same number of stressful events has a much lower risk of depression
• Low stress environments, regardless of genotype, predicted lower rates of depression
• The 5-HTT gene is correlated to depression, but only when interacting with a stressful environment
• Supports diathesis-stress model of depression

Question 4

Caspi Et Al Study (bio)

Strengths

Answer 4

• large sample size

Question 5

Caspi Et Al Study (bio)

Limitations

Answer 5

• Only demonstrates correlation, not causation
• Roughly 43% of people have the shorter alleles and not all suffer from depression
• People who do not have the 5-HTT gene also became depressed, it can be hard to conclude that genes is a major contributing factor
• Assumes that serotonin is linked to depression

Question 6

Caspi Et Al Study (bio)

Ethical Considerations

Answer 6

• Protection from harm
  
  • Contacting an information may have contributed emotional stress
  • Talking about past stressful events could bring up past traumas
• Confidentiality
  
  • Important that researchers do not share sensitive information (especially with informant)

Question 7

Caspi Et Al Study (bio)

Research Method

Answer 7

Correlation study