Biological Risk Factors (AQA A-Level Psychology): Revision Notes
Biological Risk Factors
Understanding genetic vulnerability
Genetic vulnerability refers to any inherited predisposition that increases the likelihood of developing a disorder or condition. In addiction, genes do not directly cause addictive behaviour - instead, they create a biological susceptibility that may lead to dependency when combined with environmental factors.
It's important to understand that inherited traits create predisposition rather than inevitability. An individual cannot become addicted without exposure to addictive substances, and exposure alone doesn't guarantee addiction will develop.
However, genetic factors help explain why some people progress from occasional use to full dependency whilst others do not.
Genetic mechanisms in addiction
Research has identified two main biological pathways through which genetic factors influence addiction risk:
Dopamine receptor variations
The brain's reward system relies heavily on dopamine communication between neurons. This process depends on dopamine receptors located on neuron surfaces. One particular receptor type, D2, appears especially important in addiction vulnerability.
Some individuals inherit abnormally low numbers of D2 receptors compared to the general population. Since the total proportion of different receptor types in the brain is genetically determined, this creates a biological predisposition.
People with fewer D2 receptors may experience less satisfaction from natural rewards, potentially making them more vulnerable to seeking artificial stimulation through addictive substances.
Metabolic enzyme differences
Individual differences in how efficiently the body breaks down substances also influence addiction risk. The CYP2A6 enzyme provides a clear example of this mechanism, as it's primarily responsible for metabolising nicotine in the liver.
Research by Pianezza and colleagues in 1998 revealed that some people lack a fully functioning CYP2A6 enzyme. These individuals tend to smoke less than those with normal enzyme function, suggesting they require smaller amounts to achieve desired effects.
Since CYP2A6 enzyme expression is genetically controlled, individuals with highly active enzymes face greater genetic risk of developing nicotine addiction.
Research evidence
Kendler et al. (2012) - adoption study
This large-scale study used data from the National Swedish Adoption Study to examine genetic influences on addiction development. Researchers focused specifically on adults who had been adopted away from their biological families during childhood.
Research Study: Genetic Influence on Addiction
Participants: Adults adopted in Sweden with complete family history records
Aim: To determine whether having a biological parent with addiction increases addiction risk in adopted children
Procedure: Researchers compared addiction rates between adopted individuals whose biological families included at least one addicted parent versus those with no family history of addiction
Findings: Participants with an addicted biological parent showed a 8.6% addiction rate, compared to just 4.2% among those with no family history of addiction
Evaluation - Strengths: The adoption design effectively separates genetic from environmental influences, as participants were raised away from their biological families. The large sample size from national records provides robust statistical power.
Evaluation - Weaknesses: The study relies on official records that may underestimate addiction rates. Cultural factors specific to Sweden may limit generalisability to other populations.
Indirect genetic effects
Genetic vulnerability may also operate indirectly by influencing behavioural characteristics linked to addiction risk. Traits such as self-control and emotional regulation appear to have genetic components, which can create cascading effects.
For example, a young person who inherits poor behavioural control might struggle with concentration and academic performance. Academic difficulties can lead to negative self-perception, disruptive behaviour, and association with similarly struggling peers. This social drift towards risk-taking peer groups increases exposure to addictive substances and normalises their use.
These indirect pathways mean genetic vulnerability may have greater influence on addiction development than initially apparent, as the biological predisposition shapes multiple aspects of an individual's life trajectory.
Remember!
Key Points to Remember:
- Genetic vulnerability creates predisposition to addiction rather than causing it directly - environmental exposure remains essential
- Two main biological mechanisms involve dopamine receptor variations (particularly D2 receptors) and differences in metabolic enzymes like CYP2A6
- Adoption studies provide strong evidence that genetic factors contribute meaningfully to addiction risk across different substances
- Indirect effects through behavioural characteristics may amplify genetic influence by shaping social environments and life outcomes
- Gene-environment interaction means genetic predisposition only leads to addiction when combined with appropriate environmental triggers