Caspi et al : Influence of Life Stress on depression - 3

Question 1

Influence of Life stress of depression study

Answer 1

1. Caspi et al. (2003)

2. Researched the influence of genes and life stress on depression

Question 2

Background to the Caspi et al study

Answer 2

1. Lots of research evidence has found that stressful life events cause depression, but not everyone who experiences stressful life events become depressed
2. This study looks at whether a gene linked to the neurotransmitter serotonin makes some people more likely to become depressed after stressful life events than others
3. The genes that cause someone to have lower levels of serotonin may explain why some people become depressed after stressful life events

Question 3

Aims to the Caspi et al study

Answer 3

1. The main aim was to see why stressful experiences lead to depression in some people but not others.
2. The researchers wanted to investigate the role of a gene involved with serotonin to see if it contributed to depression.

Question 4

5-HTT gene

Answer 4

A gene associated with the serotonin levels and the amount of serotonin available in the brain

Question 5

Procedure to the Caspi et al study

Answer 5

1. The study was longitudinal and therefore investigated participants at ages 3, 5, 7, 9, 11, 13, 15, 18, 21 and virtually all again at age 26
2. The participants were not recruited by the researchers but were taken from a previous study - there were 847 members
3. Divided into a short-short group, long-short group, and long-long group based on the type of 5-HTT gene they had
4. For each of the groups, the stressful life events occurring after their 21st but before their 26th birthdays were recorded using a life-history calendar. The 14 life events included employment, financial, housing, health and relationship stressors.
5. For each of the groups at age 26, the depressive symptoms for the past year were assessed using the Diagnostic Interview Schedule.
6. For each of the groups at age 26, an informant (someone who knew them well) was asked via questionnaire about depressive symptoms for the past year for 96% of the participants.

Question 6

Results to the Caspi et al study

Answer 6

1. There were no differences across the three groups in terms of the number of stressful life events experienced. This suggested that the genes did not influence exposure to stressful life events.
2. Individuals carrying an a short gene had a significantly stronger interaction between life events and self-reported depression at age 26.
3. Stressful life events predicted major depression among carriers the polymorphism of the 5-HTT gene

Question 7

Conclusion of the Caspi et al study

Answer 7

The 5-HTT gene interacts with life events to predict depressive symptoms, an increase in symptoms, diagnosis of depression, new-onset diagnoses, suicidality and an informant’s report of depressed behaviour. Those carrying a long polymorphism were less likely to develop depression or suicidality.

Question 8

Strengths of the Caspi et al study

Answer 8

1. There is a large sample of people so generalising the results are easier
2. Information is useful for doctors as it shows that there are different causes for the symptoms of depression

Question 9

Weaknesses of the Caspi et al study

Answer 9

1. evidence is self-report data so it lacks reliability as some people may exaggerate or understate their symptoms