19- Gene X Environment Interaction

Question 1

1- How Do Persons and Situations Interact?

Answer 1

1. People select themselves into different situations
2. People create situations
3. Same environment/situation can elicit different responses in
   different people

Question 2

2- What is the Diathesis-Stress Model?

Answer 2

• Genetic vulnerability model
• Negative psychological outcomes result from the interaction between:
  1. A genetic predisposition (diathesis)
  2. Stressful life events (stress)
• When an individual with a predisposition encounters a stressful life event, they are more likely to develop negative psychological
  outcomes than those without this predisposition

Serotonin Transporter (5-HTT) Gene
* Serotonin: Neurotransmitter involved in the modulation of emotions
* Serotonin transporter (5-HTT): Removes serotonin released into synaptic cleft (serotonin reuptake)
* 5-HTTLPR: Region of the serotonin transporter gene that regulates transcription of this gene
* Short (S) allele: Lower efficient transporter function - Serotonin remains in the synapse longer, is recycled more slowly, resulting in a net reduction in circulating serotonin
* Long (L) allele: Most common; Higher efficiency causing more serotonin
reuptake and less extracellular serotonin
- Ultimately more circulating serotonin

• 5-HTTLPR moderates effect of life events on depression
• People with one or more of the short allele (S) showed more symptoms of depression and greater suicidality following stressful life events vs. those with 2 copies of long allele (L)

Question 3

3- What is the Differential Susceptibility Model?

Answer 3

• Some individuals are more biologically susceptible/sensitive to both
  negative AND positive environmental conditions
• Genetic predisposition + negative events = negative outcomes
• Genetic predisposition + positive events = positive outcomes
• Not that genes make someone more “vulnerable”, but instead make them more “malleable” and “reactive” to the environment

Dandelions and Orchids
Dandelions= metaphor for LL people. thrive everywhere, not really affected by specific situations
Orchids= metaphor for sL or ss people. Die in bad or not good enough environments, but REALLY THRIVE in good environments

Diathesis-Stress vs. Differential Susceptibility
For protective genes/low malleability/LL/dandelions: in very nurturing/positive environments, in low stress environments and in high stress environment, same neutral psychological outcomes
For risk gene/high malleability/sL/ss/orchids: very nurturing/positive environment=positive psychological outcomes, low stress=neutral psychological outcomes, high stress=negative psychological outcome

Strengths of Differential Susceptibility Model
* More complete by examining what happens under positive
circumstances
- Greater reactivity/ malleability extends to positive circumstances
* From evolutionary perspective, explains why “risk” genes would have
persisted across human history
- Can confer advantage under the right circumstances

Question 4

4-
5-HTTLPR, Life Events, and Depression Revisited

Answer 4

Life events and depression
* S/s (vs. s/l and l/l) more likely to show depressive symptoms when experienced
many recent negative life events
* S/s (vs. s/l and l/l) less likely to show depressive symptoms when experienced more recent positive life events (low stress)

Childhood
* S/s most likely to show depressive symptoms if experienced childhood adversity in family
* S/s less likely to show depressive symptoms if had supportive childhoods

Neuroticism
* S/s less neurotic if experienced predominantly positive life events and more neurotic if experienced more
negative events
* Neuroticism in s/l and l/l unrelated to life events

Life satisfaction
* S/s more satisfied with life if experienced relatively more positive events and less satisfied if experienced
relatively more negative events * Life satisfaction in l/l unrelated to experienced life events

Summary of Findings with 5-HTTLPR
* Consistent with differential susceptibility, short allele is a
susceptibility/malleability factor that predicts negative outcomes in negative contexts and positive outcomes in positive contexts
- Depression
- Neuroticism
- Satisfaction with life
* Why?
* Short allele biases attention to emotional information

Question 5

6- How does it work?

Answer 5

• Why?
• Short allele biases attention to emotional information

Dot-Probe Task
ss people had a slower reaction time because their attention was biased by the emotional face
* Short allele associated with attentional bias for emotional info

5-HTTLPR and Emotion Processing
* Short allele associated with: - Attentional bias for emotional info
- More activation in brain areas associated with emotion processing (e.g.,
amygdala, prefrontal cortex)
* Differences in emotional processing and regulation may be mechanism responsible for short allele as susceptibility factor

Question 6

7- Other Malleability Genes

Answer 6

DRD4: dopamine receptor gene
* Dopamine system is involved in motivation
and reward processing
* 7-repeat allele associated with lower dopamine receptor efficiency
* Differential susceptibility: DRD4 and maternal sensitivity
- Kids with 7-repeat allele showed most externalizing
behaviour (oppositional, aggressive) when had
insensitive parenting
- BUT least externalizing behaviour when they had
highly sensitive parenting