Caspi et al (2003)

aim

to investigate the role of the 5-HTT gene in developing depression in response to stressful life events

method

• Participants were 847 New Zealand 26- year- olds

• longitudinal study

  • so, participants were tracked from ages 21-26

• correlational study

  • cuz researchers were trying to establish a correlation between the 5-HTT gene and the development of depression in response to stress

procedure

• genetic mapping was utilized to divide participants into 3 groups

  • (They were separated into 3 groups, based on the length of the alleles on their 5HTT transporter gene)

  • Group 1’s alleles of the 5-HTT gene were both short

  • Group 2 - had one short allele and one long allele

  • Group 3 - both alleles were long

• Participants were asked to fill out a “life history calendar” which assessed the frequency of stressful life events

• also completed interviews, which enabled researchers to evaluate symptoms of depression

results

• participants in group 1 - reported more depression symptoms in response to stressful life events

  • ex: if participants experienced a major stressful life event when they were 21, they tended to develop depression by the age of 26

    • only occurred if they had a short allele of the 5-HTT gene

• Childhood maltreatment was predictive of depression in adulthood only in adults with either one or two short alleles (Groups 1 & 2)

conclusion

• the 5-HTT gene plays a role in an individual’s sensitivity to stress

  • relationship between the alleles of the 5-HTT gene & the incidences of stress & depression

  • long alleles may prevent depression which arises as a result of stress

strengths

• age was controlled

• study is fairly easy to replicate

• groups were created depending on size of their alleles

  • allows researchers to identify the size of the allele which causes the behaviour

limitations

• correlation study - doesn’t allow for establishment of cause-and-effect relationship

• cannot say conclusively that stress caused depression in ppl with short alleles

  • could be other factors

• ethical concerns - ppl with short alleles may be sad or concerned to learn that their more susceptible to having depression

applications

• provides insight into biological causes for depression

• furthers investigation into alleles