Caspi et al (2003)
Cards (8)
- Aim
- See whether there is evidence for a gene-environment interaction for the mutation of the serotonin transport gene (5-HTT)
- See if serotonin transporter is involved in the reuptake of serotonin in brain synapse.
- Method
- Research method - questionnaire
- Participants aged 26 years old
- 847 participants
- Background info
- Divided into 3 groups
- Group 1: two short alleles
- Group 2: One short & One Long Alleles
- Group 3: Two long alleles
- Mutation of the 5-HTT gene has the shorter alleles
- Roughly 43% have shorter alleles.
- Procedure
- Participants filled "stressful events" questionnaire
- Asked frequency of 14 different events including financial, employment, health & relationship stressors (Life time stressors)
- All aged 26 and answer based off life events from age 21-26
- All assessed for depression.
- Results
- People who had one or more short versions of the allele demonstrated more symptoms of depression & suicidal ideation in response to stressful events
- Effect is stronger for those with three or more stressful life events (Not Naturally occurring)
- Findings
- Inheriting the gene does not lead to depression
- Inheriting the gene means when experiencing stressful life events it can cause an increased chance of depression or a different psychological reaction.
- Strengths
- Large Sample size
- Ecological Validity
- Holistic study - Measures the interaction between biological and enviornmental factors in depression.
- Weakness
- Correlation - no cause and effect
- Study assumes serotonin causes depression
- Life event info self reported
- Later studies do not show similar results - low reliability
- Some participants do not carry the gene mutation and have depressive effects - showing a lack of exclusivity