Caspi et. al 2003

biological, sociocultural

Aim

to determine evidence for GxE for a mutation of the seretonin transporter gene, 5-HTT

sample

over 800 New Zealand 26 year old members of a cohort assessed for mental health yearly since they were 21

procedure

1. divided into 3 groups based on allele length of the 5-HTT gene
   -Group 1: 2 short alleles
   -Group 2: 1 short allele, 1 long allele
   -Group 3: 2 long alleles
   (short allele = mutation)

2. had to fill out “stressful life questionnaire” → stressors + depression assessed

findings

ppl with short allele → more likely to develop MDD as a response to stressful life events

• 80% short allele = depressed after 3 or more negative life events/year

• 30% did more similar events when long allele of the 5-HTT gene

conclusion

may be a relationship between depression + genetics → support for G x E

strengths

holistic, sample size, ecological validity

weaknesses

no cause-effect → correlational study, assumes seretonin as underlying cause for depression, self-reported life events (no verification)