AO1: The Genetics of Addiction
- Initiation: insights from family and twin studies- McGue (1999) found that genes contribute to the development of alcohol dependence, with hereitability estimates between 50% and 60% for both men and women.
- In a review of studies on hereitability of illicit drug abuse and dependence, Argrawal and Lynskey(2006) found that this was significantly affected by genetic influence- heritability estimates ranging from 45% to 79%. Kendler(2003) suggests that genetic influence on alcohol and drug dependence manifests itself in a general disposition towards behavioural disorders.
- Specific genes, specific drugs- Link between D2 dopamine receptor gene(DRD2) to severe alcoholism. Noble et al found that the A1 variant of this gene was present in 2/3deceased alcoholics, whereas only 1/5 deceased non-alcoholics had the A1 variant of DRD2 gene.
- Individuals with with the A1 variant appeared to have significantly fewer dopamine receptors in pleasure centres of the brain. People who inherit the A1 variant are more likely to become addicted to drugs that icrease dopamine levels(alcohol,cocaine,heroin+nicotine) as this compensates for the deficiency by stimulating the few receptors they have= addiction maintained as only with drug they feel good.
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AO2: The genetics of Addiction
- Explaining individual differences- +Genetic explanations can explain why some people become addicted, yet others who have the same environmental experiences and life pressures do not. some people are more vunerable to develop an addiction because of their genetic predisposition. This idea of genetic vunerability may also explain why some people are more resistant to treatment for their addiction and more likely to relapse.
- Inconsistent research findings- Meta-analysis by Noble- 48% of more severe alcoholics,32% of less severe alcoholics,and 16% of controls are carriers of the A1 variant of DRD2 gene, thus supporting the claim that this gene was an important influence in development of drug and alcohol addiction. However, several subsequent studies have failed to find any relationship between alcoholism and the DRD2 gene, or have only found a very weak relationship.
- DRD2 and other disorders- Comings et al found that the A1 variant occurred in people with several disorders, including autism and tourettes syndrome. The A1 variant of the DRD2 gene was present in 45% of the tourettes patients compared with 25% of controls. This finfind creates a problem for the idea that DRD2 being a reward gene as people with tourettes and autism are not thought to b especially pleasure seeking.
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AO1: The Disease Model- role of dopamine
- Initiation- Addictive drugs stimulate a reward circuit in the brain. Rewarding experiences, such as drug taking, trigger the release of of the neurotransmitter dopamine, effectively telling the brain to do it again.e.g. crack cocaine causes a large and rapid activation of dopamine receptors in the mesolimbic pathway. Robinson and Berridge- incentive sensitisation theory- suggest that reported exposure to abusive drugs leads to increased sensitivity of the brain to their desirability.
- Maintenance- Chronic exposure to alcohol or drugs eventually leads to down-regulation. The negative state then becomes the driving force to the drug taking.e.g. the user no longer takes drugs to obtain pleasureable experience(positive reinforcement) but takes them to avoid an unpleasurable state(negative reinforcement). Drugs must be taken to avoid withdrawal symptoms(Koob and Kreek).
- Relapse- Desire for the drug becomes more important than most other desires. Addicts have learned to expect a rewarding experience from the drug, and for the individual trying to obstain from it, they are surrounded by cues.e.g. reminders of the drug that cause the release of dopamine and therefore predict a reward.
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AO2: The role of Dopamine
- Supporting research evidence- Volkow et al gave Ritalin,which lifts dopamine levels, to a group of adult volunteers.Some of them loved the drug while the others hated the way it made them feel.Those who loved the rush had fewer D2 receptors than those who hated it.They concluded that some people are particularly vunerable to the added rush of dopamine,but others have a circuitry that cant take the additional stimulation.This would explain why some people after experimenting the first initial experience will become addicted and some would not.Limitations of neurochemical explanations- Neurochemical explanations ignore other causal factors including the social context of alcohol or drug taking behaviours,but offer treatment by various pharmological methods.
- Are dopamine sensitivity and addiction inevitability linked?- An experiment with monkeys conducted by Grant et al showed that the dopamine system can be influenced by social interactions.Animals that lost social status also lost D2 receptors.Volkow et al claims that people who grow up in stimulating surroundings are protected against adiction. She argues that even if people dont have a naturally responsive dopamine system,if they have more chances to get excited by natural stimuli,they are less likely to need artificial boost.
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- The value of animal research- Researchers have discovered animal preferences for the same drugs that humans use in socially problematic ways. Hockam and Redelmier argue that high quality animal studies rarely replicate in human research. Banks et al used monkeys to establish the feasibility of treating cocaine addiction by substituting a less addictive replacement drug that minimises the action of cocaine. The value of this research is that it duplicates what has been found in smaller human studies, suggesting monkeys have a useful role to play in testing effectiveness of potential treatment for addiction in humans.
- Reductionism- Biological explanations of addiction are reductionist as they reduce a complex phenomenon such as addiction down to a relatively simple level of explanation.i.e. imbalance of brain chemicals. While there are potential advantages to this approach such as studying the amily history of addiction or offer possibilities of treatment, but it also has its limitations. Reducing addiction to just the action of genes or chemicals ignores all other potential influences(e.g.irrational thought procresses, social context).
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