Genetic factors Flashcards
What did Coccaro et al. study?
Studied adult male monozygotic and dizygotic twins.
Why are monozygotic (MZ) twins expected to show higher similarity in aggression than dizygotic (DZ) twins?
MZ twins share 100% of their genes
DZ twins share 50%.
If aggression is genetically influenced, MZ twins should be more similar in aggression.
What were the concordance rates for direct physical assault?
MZ twins: 50%
DZ twins: 19%
What were the concordance rates for verbal aggression?
MZ twins: 28%
DZ twins: 7%
What did Rhee & Waldman find in their meta-analysis of adoption studies?
Genetic influences accounted for 41% of the variance in aggression, supporting twin study findings.
What does the MAOA gene do?
It controls the production of the enzyme MAO-A, which regulates serotonin levels.
What is the MAOA-L variant, and how is it linked to aggression?
MAOA-L (low-activity variant) results in reduced MAO-A enzyme activity, leading to higher aggression levels.
Why is MAOA-L sometimes called the “warrior gene”?
Lea & Chambers found 56% of New Zealand Māori men had the MAOA-L variant, compared to 34% of Caucasians. Māori people historically had a reputation as fierce warriors.
What did Brunner et al. study?
28 men
Dutch family
history of violent impulsive crimes (rape, attempted murder, assault).
What did Brunner et al. discover?
These men had abnormally low levels of MAO-A due to the MAOA-L variant, leading to what is now called Brunner Syndrome.
Why do genes alone not determine aggression?
Genes interact with the environment. The MAOA-L gene is linked to aggression only when paired with early-life trauma.
What did Frazzetto et al. find about MAOA-L and early trauma?
MAOA-L carriers + early trauma = High aggression
MAOA-L carriers without trauma = No significant aggression increase
