ADDICTION: Bio - Addiction Genes A01

Question 1

Addiction Genes Intro

Answer 1

Biological view to addiction

• Explains why some people become addicted to addictive behaviours and others do not

Goldman et al. - Addictions = moderately - highly heritable

Heritability ranges from +0.39 Hallucinogens to +0.72 Cocaine

Question 2

Addiction - DRDR Gene

Answer 2

D2 DOPAMINE RECEPTOR GENE

A1 Variant:

Fewer dopamine receptors in the brain’s pleasure centre; lower pleasure response to normally adaptive behaviours (eating / drinking / sex)

• Individuals try to compensate low dopamine levels by overstimulating through engagement in addictive behaviours / substances

Comings et al. - 49% of smokers & ex smokers carried A1 variant - 26% of non-addicts carried A1 variant

Question 3

Addiction - ADH & ALDH Gene Overview

Answer 3

ADH & ALDH: responsible for how alcohol is metabolised by the body

⭐Body normally metabolises alcohol into acetaldehyde due to the enzyme alcohol dehydrogenase (ADH); enzyme acetaldehyde dehydrogenase breaks it down further into acetic acid & water⭐

Question 4

What do ADH & ALDH genes do?

Answer 4

decrease alcoholism by increasing acetaldehyde in body
- Leads to unpleasant reactions to alcohol
- Flushed face
- Nausea
- Individual is less likely to drink from these reactions & so are less likely to become addicted
- Reaction is found in larger concentrations among East Asian cultures
- May explain lower alcohol consumption rates in these cultures
- Some variants of ADH & ALDH increases alcoholism

Question 5

Addiction Genes Ojelade et al.

Answer 5

Rsu1 gene, when not functioning properly, lowered fruit fly’s sensitivity to alcohol

• Found a relationship between the gene and alcohol dependence in humans

Question 6

Addiction Genes: Twins and Adoptive Studies

Answer 6

TWIN STUDIES: used to demonstrate the influence of genetic factors in addiction

Kendler & Prescott - interviewed ~2000 twins & found that
- Environmental & social factors influenced whether a person would initiate cocaine use
- Genetic factors determined whether the person became addicted

→ Genetics influence maintenance but cannot explain initiation

Question 7

Addiction: Kendler & Prescott

Answer 7

interviewed ~2000 twins & found that
- Environmental & social factors influenced whether a person would initiate cocaine use
- Genetic factors determined whether the person became addicted

→ Genetics influence maintenance but cannot explain initiation

Question 8

Addiction Genes: Diathesis-Stress Model

Answer 8

Suggests that a disorder such as addiction only develops when a genetic predisposition is triggered by an environmental stressor

• Serotonin transporter gene (5HTT) has also been linked to the development of alcoholism but not solely
  
  • Appears to interact closely with environmental factors such as maltreatment in childhood (Kaufman et al.)