Lecture psychiatric disorders 14: bright side of mental illness - Neurobiology of Resilience Flashcards
What was the conclusion of the Caspi study where they looked into the probability of major depression in association with the number of stressful life events and polymorphism for the serotonin transporter gene (5-HTT)?
(Just to clear up: there are three variants for this gene: SS, SL or LL)
That polymorphism for the SS variant resulted in the highest probability of depression when the number of stressful life events increased. The LL variant had the lowest probability (resilient?)
Note: this was only the case when there were stressful life events. The SS variant does not increase the chance of depression by itself.
What are other disadvantages when you carry the short version of 5-HTT (S/S or S/L)?
Anxiety, neurotic behavior, higher stress-vulnerability and increased probability of smoking, drinking and gambling.
What are risk genes of dopamine genes and what risk is increased?
DRD2, DRD4, dopamine transporter 1 and MAO-A low acitivity gene variant.
There’s an increased risk of ADHD, externalizing behaviors (such as aggression and conduct disorder) and antisocial personality disorder.
What was the conclusion of the other study by Caspi et al. that looked into the probability of developing antisocial behavior in association with childhood maltreatment and one of the MAO-A variants (high or low acitivty)?
- The risk for developing antisocial behavior was high when the person carried the low activity MAO-A gene and had severe childhood maltreatment.
- When there was no childhood maltreatment, it didn’t matter whether someone had the high or low MAO-A gene activity.
What’s interesting when you compare the two graphs of the two different studies by Caspi et al.?
That the genes that are termed as risk genes, are only risk genes when there are stressful life event or childhood maltreatment. But when there’s no childhood maltreatment or stressful life events, these genes seem to be protective.
What’s the problem with these graphs?
That they only look at negative life events, it’s either having stressful life events or none and it’s either having childhood maltreatment or not.
So what would happen if we extent the x- and y-axis, where we also could look at the positive events in life.
Even though these graphs only show the negative life events and how certain gene variants influence this negatively, carriers of the S/S or S/L variant of 5-HTT do have advantges. What advantages are there for these S-variant carriers?
They are better at decision making, impulse inhibition, risk avoidance and social conformity (and also creative dancing).
The same phenomenon depicted in this graph is also seen for a specific gene variant of the dopamine receptor D4.
What gene variant of the dopamine receptor is this and how does it influence a person?
Note: i mean with phenomenon the fact that certain gene variants affect life negatively or positively only when there are negative or positive life events.
The dopamine receptor D4 7-repeat (DRD4-7R).
If you carry this gene variant, the chances of developing ADHD, aggressiveness and anti-social behavior increases. Only:
- When you have an insensitive mother, these chances of more behavioral problems increase significantly, compared with children who have a sensitive mother.
What is the differential susceptibility to environment hypothesis?
The idea that risk genes that increase the risk of certain disorders when negative life events occur, may also protect you when life events are positive.
What does the differential susceptibility to environment hypothesis tell us?
That a majority of children is resilient to positive and negative life events (early in life). But there’s also a minority of children that are more susceptible to both positive and negative life events (early in life), which is for better and worse since the brain is supersensitive to all experiences.
What is the orchid hypothesis?
It’s based on the differential susceptibility to environment hypothesis and says that:
- most of us are dandelions → they have genes that makes them hardy and resilient. These people are able to take root and survive almost anywhere.
- a few of us are orchids → they have genes that make them fragle and fickle. These people, like orchids, are vulnerable and difficult to grow, but capable of blooming spectacularly if given greenhouse care.
Don’t think this is really important, but it’s interesting!
What is also seen in children that carry the DRD4-7R variant of the dopamine receptor?
Children with secure attachment (family) donated more money to charity, but only if they carried the DRD4-7R variant!
What is seen in children with normal temperament (dandelions) and in children with difficult temperaments (orchids) in regard to quality childcare?
The degree of quality childcare does not influence the behavior of children with a normal temperament, but it does influence children with difficult temperaments.
This means that when the degree of quality childcare is high, the behavior of these children with difficult temperaments is better. But when the degree of quality childcare is low, the behavior of these children is worse.
This supports the differential susceptibility hypothesis.
What does this model show?
(On the x-axis the environment goes from negative to positive and on the y-axis the outcome goes from negative to positive).
That people who carry risk genes and are thus highly susceptible to environmental influences, have an increased positive outcome when the environment is more positive. The people who lack these risk genes, have a low susceptibility to the environment, and thus the outcome is not influenced.
What happens if this graph is extended on the x- and y-axis?
There would be crossing of the lines of the people with low and high susceptibility to environmental factors. This means that if environmental factors get more positive, the people that are highly vulnerable to these influences get a greater advantage (more developmental enhancement). While this doesn’t chance for the group that is not susceptible to the environment, so these people get no developmental enhancement.
Increasing the x- and y-axis, results in the appearance of the differential susceptibility to environment hypothesis.
