Addiction Genes

Question 1

If there’s a role for genetics this explains why not all become addicted. How?

Answer 1

• Genes may affect response to addictive behaviours.

Question 2

If genes are involved, those who are (blank) should share the behaviour.

Answer 2

• Closely related.

Question 3

How did David Goldman et al (2005) describe the heritability of addictions and what did he find?

Answer 3

• ‘Moderately to highly heritable.’
• Heritability of hallucinogens = +.39
• Heritability of cocaine = +.72

Question 4

Specific genes have been associated with addiction. Name these genes.

Answer 4

• DRD2 Genes.

- ADH Genes.

Question 5

What does DRD2 stand for?

Answer 5

• D2 Dopamine Receptor Gene.

Question 6

A1 Variants of the DRD2 Gene have fewer what?

Answer 6

• Fewer dopamine receptors in brain’s pleasure centre.

Question 7

What is the ‘pleasure centre’?

Answer 7

• Part of the mesolimbic pathway.

- Provides pleasure in response to normally adaptive pleasurable behaviours (eating + sex).

Question 8

Those with the A1 Variant who lack in dopamine receptors compensate in other ways. How?

Answer 8

• Overstimulation: engaging in addictive behaviour.

Question 9

The A1 Variant of the DRD2 Gene is implicated in many behaviours. Give 2 examples.

Answer 9

• David Comings et al (1996):
• 48.7% smokers and ex-smokers had A1 Variant VS 25.9% general population.
• 50.9% gambling addicts had A1 Variant VS 25.9% general population.

Question 10

What are ADH and ALDH traits responsible for?

Answer 10

• The process of how alcohol is metabolised by the body.

Question 11

How is alcohol normally metabolised by the body?

Answer 11

• Metabolised into acetaldehyde due to enzyme called alcohol dehydrogenase (ADH).
• Further broken down into acetic acid and water by enzyme called acetaldehyde dehydrogenase (ALDH).

Question 12

Some variants of ALDH and ADH genes decrease alcoholism risk. How? What does this cause?

Answer 12

• By increasing acetaldehyde levels in the body.

- Unpleasant reactions to alcohol (facial flushing + nausea).

Question 13

Where are the unpleasant reactions to ALDH + ADH genes commonly found?

Answer 13

• Larger concentrations among East Asian populations which may explain lower alcoholism rates.
• Experience is unpleasant so don’t want to do it again.

Question 14

Variations of ADH genes have been linked to increased alcoholism risk. How?

Answer 14

• Body may break down alcohol at a slower rate meaning that individual is more likely to drink more and potentially become addicted.

Question 15

Where are lower activity variants of ADH genes commonly found?

Answer 15

• Oriental populations.

- Associated with increased risk of alcohol dependence (Higuchi et al, 2006).

Question 16

Where do ADH4 variants affect alcoholism risk?

Answer 16

• European populations (Edenberg et al, 2004).

Question 17

What is the Diathesis-Stress Model?

Answer 17

• The idea that a disorder develops when a genetic predisposition to a particular disorder is triggered by an environmental stressor.

Question 18

Why must we consider the Diathesis-Stress Model?

Answer 18

• It’s too simplistic to say that biological factors (genetics) are the only cause for addiction.

Question 19

Explain the workings of the Serotonin Transporter Gene (5HTT) in correlation with the Diathesis-Stress Model.

Answer 19

• 5HTT linked to alcoholism but not alone; interacts closely with environmental factors, such as maltreatment in childhood (Kaufman, 2007).