Bio etiology

Question 1

Silberg aim

Answer 1

to investigate what causes the differences in heritability of depression in males and females

Question 2

Silberg procedure

Answer 2

• depressive symptoms were assessed using the Child & Adolescent Psychiatric Interview
  
  • this interview is administered to both twins & at least 1 of the parents
• list of 39 potentially stressful past-year life events was created
  
  • included events such as failing a grade, losing a close friend through arguments
• ratings for these interviews for these events were obtained in interviews w the mothers

Question 3

Silberg results

Answer 3

• life events most associated w depression were similar in boys & girls
• boys & girls have similar levels of depression before the age of 12, but girls’ rates of depression increase significantly faster after the age
• analysis showed that stressful life events had a greater impact on depressive symptoms of girls than boys, especially during & after puberty

Question 4

Silberg conclusion

Answer 4

• the effect of negative life events on depressive symptoms in adolescent girls is stronger than boys
• this suggests a genetic predisposition to experiencing particular stressful life events
  
  • other words → girls have a genetic predisposition that make them for vulnerable to stressful events at least in adolescence

Question 5

Gene-environment correlation

Answer 5

• gene environment interaction (GxE) describes the situation when individuals w different genetic predispositions react differently to the same environment
  
  • the reality is more complex bc genetics can also*influence the environment itself→ this is gene-environment correlation & there are 3 types:
    • passive rGE, evocative rGE, active rGE

Question 6

Passive rGE

Answer 6

• this is when parents pass on to the child both the genes* & some corresponding environment, so genes & environment are not entirely independent
  
  • e.g parents may give child a genetic predisposition to depression as well as a highly demanding environment that places the child under a lot of stress

Question 7

Biological explanations other than genetics - neurotransmitters

Answer 7

• number of studies have been done to establish the role of neurotransmitters in depression by comparing depressive symptoms in clients w varying concentrations of neurotransmitters in the brain
• serotonin is amongst one of the most influential neurotransmitters on depression, and the idea that its imbalance in the brain is a factor that causes depression is known as the ‘serotonin hypothesis’
  
  • this has been supported by evidence of 2 types
    
    1. certain drugs that were known to deplete levels of serotonin in the brain were also found to have depression-inducing effects
    2. certain drugs that were known to increase the levels of serotonin in the brain were also found to relieve symptoms of depression
       
       • e.g class of drugs → selective serotonin reuptake inhibitors were shown to be effective against depression
         
         • SSRIs prevent reuptake of excessive serotonin from the synapse, increasing its concentration in the synaptic gap

Question 8

Genetic factors

Answer 8

• heritability cannot be measured directly but it can be estimated from data such as twin studies, adoption studies & molecular genetics
• falconer model has been used to estimate heritability in twin studies
  
  • In twin studies, the Falconer model is used to estimate heritability - assumes that phenotype is comprised of 3 types of influence
  • Kendler et al