Genetic Factors Flashcards
(14 cards)
Twin studies
Several twin studies have shown that heretability accounts for 50% of the variance in aggressive behaviour
Twin study findings
Coccarobet al
- studies adult male MZ and DZ twins
- direct physical agg was defined as physical assault, concordance rates MZ=50% , DZ=19%
Verbal agg, concordance rates MZ=28%, DZ=7%
Adoption studies
Similarities in agg behaviour between adopted child and bio parent suggests genetic influence
- Rhee and Waldman
Rhee and Waldman findings
Meta-analysis of adoption studies of direct agg and antisocial behaviour
- found genetic influences account for 41% of the variance in agg
MAOA
An enzyme, whose role is to mop up neurotransmitters in the brain after a nerve impulse has been transmitted
- breaks down the neurotransmitter
- production of enzyme is determined by MAOA gene
- dysfunction in the gene may lead to abnormal activity of the MAOA enzyme which affects levels of S in the brain
MAOA gene
One variant of the MAOA gene nicknamed the ‘warrior gene’ leads to low MAOA activity and has been associated with various forms of agg
Brunner MAOA study
Studied 28 male memebers of a Dutch family who were repeatedly involved in impulsively agg violent criminal behaviours such as rape
-found these men had abnjormally low levels of MAOA in their brains and the low activity version of the gene
Stuart et al
Studied 97 men involved w IPV (intimate partner violence) who were part of a betterer treatment programme
- men w low activity MAOA found to be the most violent perpetrators of IPV
- engaged in highest levels of physical and verbal age and inflicted the worst injuries
Gene-environment interaction (GxE)
Low MAOA gene activity is only related to adult agg when combined w early traumatic life events
Frazzetto et al
Found an association between higher levels of antisocial agg and the low activity variant in adult males
- only the case I those who had experienced abuse by 15 y/o, those who didn’t, didn’t have particularly high levels of agg as adults even if they possessed the low activity variant
Supporting evaluation for the role of the MAOA
- Mertins et al
- Animal studies
Mertins et al
If low activity version is associated w more agg, then opposite should be true.
- Mertins et al, studied pts w low activity and high activity genes in a money distributing game
- ppt had to make decision ab whether or not to contribute money for the good of the group
- found high activity were more cooperative and made fewer agg moves than the low-activity
Animal studies
Idea that MAOA has role in agg started w mice
- Godar et al showed that MAOA knockout mice had significantly increased S levels in the brain and are hyper-aggressive
- when S was blocked by the drug fluoxetine, mice reverted to non-agg behaviour
Opposing evaluation for genetic factors
Reductionist
Just bc gene is present doesn’t mean it will be expressed
- only expressed if triggered by environment
- McDermott et al found ppt w low activity were agg only when provoked, otherwise less or same agg as control
