Caspi et al (2003)

• Aim: 

  To investigate the interaction between gene mutation (5-HTT allele) and stressful life events in major depressive disorder.
• Method: 

  Longitudinal study with a correlational design.
• Participants: 

  847 New Zealand 26-year-olds.
• Procedure:

  • Participants grouped by 5-HTT alleles (two short, one short/one long, two long)
  • Completed "Stressful life events" questionnaire
  • Assessed for depression symptom
• Results:

  • Individuals with one or more short alleles showed more depression symptoms in response to stressful events
  • Stronger effect with more stressful events
  • Gene-environment interaction increased likelihood of depression
• Strengths:

  1. Longitudinal design allowed examination of gene and life events over time
  2. Supported theory of gene-environment interaction
  3. Groundbreaking study on specific gene (5-HTT) and behavior (depression)
• Limitations:

  1. Correlational design limits causal conclusions
  2. Self-reported life events may introduce bias
  3. Not all participants with gene mutation developed depression
• Conclusion:

  The study demonstrates a gene-environment interaction in depression. Individuals with the short version of the 5-HTT gene are more likely to develop depression when exposed to stressful life events, while those with the long version show more resilience. This suggests that genetic makeup moderates an individual's response to environmental stressors, highlighting the complex interplay between genes and environment in mental health outcomes. The research helps explain why some people are more vulnerable to depression in response to stress than others.