(3) biological - genetics

give a general overview of the genetic explanation of addiction

• Helps to understand why people can engage in addictive behaviours but not all become addicts.

• The difference could be explained by variations in the genetic make up of individuals. Perhaps some carry genes that make them more prone to developing addiction

What did Goldman et al state

• if genes play a role, those more closet related should share the behaviour.

• He said addictions were moderate to highly heritable. Heritability of addictions range from +39 hallucinogens to +72 for cocaine. There isn’t 1 single gener that explains vulnerability to addiction, many have been identified, DRD2 gene + ADH gene (involved in breakdown of alcohol)

A01 DRD2 gene: what has been found in those with the A1 variant of the DRD2 gene

They appear to have fewer dopamine receptors in the area of the brain that provides us with a sense of pleasure in response to normally adaptive behaviours.

A01 DRD2 gene: why might individuals with A1 variant of DRD2 gene be more likely to engage in addictive behaviours

The lower number of dopamine receptors in these individuals means they try to compensate for this by overstimulation through engaging in addictive behaviours.

AO1 DRD2 gene: what is a key study

Comings et al: found 49% of smokers + ex smokers carried the A1 variant of DRD2 gene compared to 26% of general pop. Similar results were found with gambling addicts where 51% of them carried the A1 variant of the DRD2 gene compared to 26% of non addicts.

A01 ADH gene: what is the responsibility of the ADH genes and how does this process work

For the process of how alcohol is normally metabolised in the body, normally it metabolises alcohol due to an enzyme called ADH yet certain variants of the ADH gene have been found to effect the metabolism process.

A01 ADH gene: how have ADH genes been linked to increasing risk of addiction

Some variants of ADH gene have been linked to increase risk of alcoholism as less of the ADH’s enzyme is produced, therefore slowing down the metabolism process. Alcohol is broken down at a much slower rate meaning the individual is not so easily affected by alcohol. This can lead to them drinking more + potentially becoming addicted.

A01 ADH gene: how has ADH genes been linked to decreasing risk of alcoholism

Other variants of the ADH gene have been linked to decreased risk of alcoholism by increasing the production of the enzyme that breaks down alcohol. This means the individual experiences more unpleasant reactions to alcohol, such as facial flushes and nausea. This reaction is found in larger concentrations among East Asian populations and may help explain lower rates of alcoholism in these cultures. If an individual finds the experience of drinking so unpleasant that they do not want to do it again, they are less likely to become addicted

What is the diathesis stress model

It’s too reductionist to assume that genes can influence the development of addiction alone, we must consider the interaction that genes have with environment that may lead to addiction instead. For eg, research has found the serotonin transporter genre has been linked with the development of alcoholism but not on its own. It appears to interact closely with environmental factors such as maltreatment in childhood (kaufman et al)

A03: ✅ supporting evidence

• Comings et al + Kendler + Prescott: interviewed 2000 female twins. Found that heavy use of drugs including cocaine was more dependant on genetic factors than environmental.

• Concordance rates for dependency of drugs: MZ - 35%, DZ - 0%. This provides evidence for role of genes in addiction.

A03: evaluation of Comings et a + Kendler + Prescott supporting evidence

✅ ethical, used interviews

❌ low population validity, participant variables, no generalisability

❌ social desirability bias

❌ low historical validity

A03: Reductionist

Reductionist to claim that any addiction is due to genes when there’s many side factors involved at different phases of the process. A diathesis stress explanation may be deemed as more effective considering nature and nurture.

• Gene explanation has been critiqued for ignoring social/cultural factors (eg, changing social attitude to women’s smokers may influence likelihood of genetic predisposition).

A03: determinism + ethics

Assumed behaviour is determined with no free will. Suggests they couldn’t have controlled addiction.

It could also be considered unhelpful for addictions, Lewis (neuroscientist/ex addict) suggests labelling addiction as a disease damages the self esteem of an addict + makes them feel helpless. Could also lead to addiction less likely to take responsibility which is important if they want to over come addictions

A03: application to methods of modification

A new field in genetic research into addiction is pharmacogenetics. This is the investigation of how genetics can affect responses to medicines.

• E.g. Naltrexone is often used to treat alcoholism, but research suggests it is more effective in those with a specific gene mutation. Those with the mutation had fewer relapses.

• Although relatively expensive, it may be possible to carry out gene mapping on individuals to work out which medications are likely to be most effective