Bio Explanation 2- Addiction Genes Flashcards
Heritability - Goldman et Al (2005)
Hallucinogens +.39
Cocaine +.79
0= genes do not contribute at all to individual differences
1= Genes are the only reason for individual differences
On average 72% of the individual differences that we observe in cocaine is down to the genetics of a person.
What is the DRD2 gene?
Dopamine receptor gene.
Everyone has the DRD2 gene
Only some people have the A1 variant of the gene
What is the A1 variant of the DRD2 gene?
Fewer dopamine receptors in Nac (pleasure centre)
This means less dopamine in the brain.
How does the A1 variant lead to addictions?
People try and compensate for lack of dopamine by engaging in addictive behaviour to overstimulate the brain so they get more dopamine.
Comings et Al (1996) -DRD2 gene
Smokers - 48.79% had A1 variant
Non-smokers - 25.9% had A1 variant
Gamblers - 50.9% had A1 variant
Non- gamblers - 25.9% had A1 variant
What do ADH genes do to alcohol?
ADH breaks down alcohol to acetaldehyde (hangover).
ALDH breaks down acetaldehyde into Acetic acid and water.
What do some variants of ALDH and ADH genes do?
Some variants of the ALDH and ADH genes cause an increase in levels of acetaldehyde in the body.
Acetaldehyde causes unpleasant reactions to alcohol such as facial flushing and nausea.
This gene variant is found in large concentrations amongst East Asian populations.
Some variants decreases the activity of the ADH and ALDH genes, reducing the negative effects of drinking. This means that they are more likely to keep drinking, and become an alcoholic.
What is the diathesis- stress model?
Genetic factors interact with the environment.
An addiction only develops when a genetic predisposition is triggered by an environmental stressor.
Kaufman et Al - diathesis- stress model
The serotonin transporter gene (5-HTT) has been linked to the development of an alcohol addiction, but not on it’s own.
It appears to interact with environmental factors such as maltreatment in childhood.
