Caspi et al. (2003)

Aim

To determine whether there is evidence for a gene-environment interaction for a mutation of the seretonin transporter gene 5-HTT and depression.

Participants

847 New Zealand 28 year olds

part of cohort which was assessed for mental health on a every 2 year basis until they were 21.

Method

participants split into 3 groups based on their seretonin transporter gene alleles

1. two short alleles

2. One long one short allele

3. two long alleles

The mutation of the 5-HTT gene is characterized by shirt alleles.

all participants filles out stressful life events questionaire, which asked about frequency of 14 different stressors, including financial, employment, relationship, and health stressirs between the ages of 21-28

participants were also assesed for depressive symptoms

Findings

Participants with one or two copies if the short allele exhibited more depressive symptoms, diagnosable depression and suicidal ideation in relation to stressful life events than individuals with long alleles.

Use

This suggest that participants with the 5-HTT gene mutation have an increased genetic vulnerability to developing depressive symptoms. Stressful life events had a greater impacts on participants with the mutation to developing depressive symptoms.

Strengths

High replicability (controls) later studies found similar results

Longitudinal study —> monitor participants over time, observe changes in behaviour (eg development of depressive symptoms.)

Limitations

Correlational analysis showed relationship between allele and depressive symptoms, correlation doesnt equal causation

Self report data on life events, those who tend toward depression may remember negatove life events more

some ppl without mutation developed depression therefore genetic vulnerability alone cannot be cause/ only explanation of depression.