Biological Model of Addiction

Emphasises the influence of genetic neurochemical factors in the outset + maintenance of addictive behaviours, e.g., having parents who are alcholics or who use drugs of abuse.

Habitual use of alcohol or drugs characterises as a disease= irreversible changes in the brain chemistry in those who use substances repeatedly. 

Neurotransmitter, dopamine, subject of a lot of research into many different types of addictions. 

> Heritability estimates of 50 +60% for both men and women (McGue 1999)

>Meta Analysis: found heritability of illicit drug abuse + dependence significantly affected by genetic influence

> Family and twin studies demonstrate genes contribute to development of alcohol dependence

> Twins have also established that co-occurrence of some disorders are influenced by genetic factors

>Kendler et al (2003) analysed data from Virginia twin registry and found common genetic factor contributed to total variance in alcohol dependence, illicit drug use + dependence, and adult anti- social behaviour --> Findings: significant proportion of genetic influences on alcohol and drug dependence manifests itself in general disposition towards behavioural disorders which may lead to alcohol dependence.

• 1990s, research into DRD2 to severe alcoholism
• Nobel et al - A1 variant of gene present in more that 2/3 of deceased alcoholics, only 1/5 of deceased non-alcoholics carried A1
•  et al- increased prevalence rate of A1 variant among children born to alcoholics.
• Individuals with A1 appeared to have significantly fewer dopamine receptors in pleasure centres of the brain
• People who inherit A1 variant of the gene more likely to become addicted to the drugs that increase dopamine levels as this compensates for deficiency by stimulating the few dopamine receptors they possess
• Addiction therefore maintained because it is only with that drug they feel good.
• Comings et al- Smokers had significantly increased incidence of A1 variant of gene among smokers and ex-smokers. Among this group, 48.1% carried out A1 variant of DRD2 gene compared to 25.9% of general population. Men with variant of gene stared smoking earlier and had shorter periods of abstinence from smoking.
• A1 Variant of Gene has been limited as variety of addictions including cocaine, heroin and nicotine. 

Genetic explanations can explain why some people become addicted yet other who have some environmental experiences and life pressures do not

Some people are more vulnerable to develop an addiction because of their genetic disposition (diathesis stress model.) This idea of genetic vulnerability may also explain why some people are more resistant treatment for their addictive behaviours + more likely to relapse.

Valkrow et al (2001) gave Ritalin which gently lifts dopamine levels to a group of volunteer. Some of them loved the feeling of the drug, others hated the way it made them feel.

Neglect other possible determining factors in outset and maintenance of addictive behaviours, e.g. having parents who are alcoholic or who use drugs of abuse.