BA etiology

Question 1

Genetic explanation of depression

Answer 1

• Proposes that genes can influence a specific physiological or psychological characteristic
  and one’s susceptibility to developing depression.

-Depression is a polygenic trait, meaning that it is influenced by multiple genetic factors, it cannot be attributed to a single gene.

• Genes do not act in isolation but interact with environmental stressors that may trigger their expression through epigenetic alterations, thus increasing one’s likelihood of developing depression.
• ## This is linked to the 5 HTT gene which is a serotonin transporter, specifically involved in the uptake of serotonin from the synapse.
• The relationship between both factors has been studied through twin and kinship studies, enabling researchers to determine the extent to which psychological traits run in the family.

Question 2

Caspi et al

Answer 2

Aim: investigate the role of the transporter gene 5 HTT in depression and genetic inheritance.
- It aimed to deduce which alleles are linked to a higher or lower risk of developing MDD.

Sample: New Zealand participants which had their alleles measured and were grouped according to either having: two short alleles, two long alleles and one short and one long.

Procedure:
- Conducted a quasi-experiment, which used a longitudinal design, testing the participants every few years from the age of 3 to the age of 26.
- A correlational analysis was then conducted between allele length and depression and stressful life events.
- Were then given a questionnare to record their stressful life events that could trigger MDD and assess for depressive symptoms

Results:
-Showed that participants with 2 short alleles had more depressive symptoms in response to stressful life events comparison to those with long alleles .
- This meant that the 5 HTT gene when interacting with stressful life events means that individuals have an increased risk of developing depression and those with two short alleles have a higher risk.
-The association between the gene variation and psychological responses to childhood maltreatment was also tested.

Question 3

Limitations Caspi

Answer 3

Correlational: no cause-effect relationship
Assumes serotonin causes depression
Self reported: May not recall negative life events as easily, more recall of them could tend more towards depression

Strengths: acknowledges biological and environmental factors that may trigger MDD, more holistic approach
Longitudnal

Question 4

Ethical considerations of Caspi

Answer 4

Observational nature of longitudinal studies: researchers don’t interfere with participants’ life. By not intervening it can be argued that the study failed to protect children from harm.

On the other hand, by screening and identifying vulnerable people clinicians would be able to target people that could benefit most from psychological interventions.
Such interventions could help people with genetic vulnerabilities cope with stressful life events.

Question 5

Kendler et al

Answer 5

Aim: determine the role of genetics in depression Sample: 15,500 twin pairs. Procedure:
- A team of interviewers conducted telephone interviews to assess lifetime major depression using the modified DSM-IV criteria.

Results:
- Female MZ twins had a concordance rate of 0.44 whereas the concordance rate for female dizygotic twins was 0.16. Furthermore, male monozygotic twins had a higher concordance rate of 0.31 than male dizygotic twins with 0.11.
MZ twins have a higher concordance rate than DZ twins in both males and females.
This study demonstrates that depression does have an important genetic component due to the significantly higher concordance rate in MZ twins than DZ twins.

Question 6

Limitations of Kendler

Answer 6

Since the concordance rate between MZ twins was not 100 percent, it may be that some environmental factors may have a protective effect against depression which prevents the expression of those genes associated with the disorder.
This is an important factor since genes can only influence the onset of a behavioral trait to a certain extent and require certain environmental stressors to cause the behavior.

Due to the large sample size, the study benefits from a high external validity which strengthens the reliability of its results.

Yet, as it is purely correlational, no cause-and-effect relationship can be determined and no particular genes were tested, underscoring one of the genetic explanation’s weaknesses.

Question 7

Limitations of BA

Answer 7

• Inability to study genes in isolation. This hinders the identification of specific genes associated with depression, hence making it hard to understand how they interact with each other and which one has more significant than others.

-Because of this, genetics alone cannot explain why individuals with no family history of depression still develop the disorder, thus demonstrating that depression cannot be studied through a single lens, but rather through an integrative approach of social, cognitive, and biological factors.