The genetics of addiction:
* People who have an addictive personality are likely to be predisposed to it because of their genes. * Family and twin studies have demonstrated that genes contribute towards the development of alcohol dependence, with heritability estimates of between 50 and 60 % for both males and females. McGue, 1999 * Fowler et al, 2007 – found that in a study of 1,214 twins genetic influences played a role in the progression to heavy addiction. * Agravel & Lynsky 2006 – genetic influence with heritability estimates ranging between 45 and 79% * Kender et al, 1998 – 1934 female twins. Drug addiction was mainly due to genetic factor. * Multiple genes are involved and different genes underlie different addictions: Lerman and Commings research indicates this. * A1 Variant of the DRD2 Gene: Individuals with the A1 variant appear to have fewer dopamine receptors in the pleasure part of the brain making it known as the 'Reward Gene' This means that even a little bit of dopamine would cause a lot of pleasure for these people. * A study looking at smokers found that a significantly higher number of smokers had the A1 variant at 48% where as 29% of the rest of the population did.
The Disease Model:
* Dopamine affects pleasure and emotion; addictive substances cause the release of this. A dopamine pathway is the mesolimbic pathway, which releases dopamine into the limbic part of the brain. People who are prone to addiction naturally have a more sensitive mesolimbic pathway. * Initiation – Research has shown that addictive drugs stimulate a reward circuit in the brain, the drug taking triggers the release of dopamine into the brain which acts as an incentive, effectively telling the brain to ‘do it again’. * Maintenance – Chronic exposure to drugs, alcohol etc. eventually causes a decrease in the activity of these reward circuits,...