Biological explanations and treatments of addiction
Assumptions of the biological or medical model of addiction are
· Addiction is an illness
· Addiction is a specific diagnosis, you are either addicted or not, you can’t be slightly addicted.
· Problem lies in the individual
· Addiction is irreversible
· The individual is not to blame for their addiction
· An emphasis on treatment
Some biologists believe that people who show addictive behaviour have an underlying physiological abnormality which predisposes them to addiction. Groups such as Alcoholics anonymous take the view that addiction is like an allergic response.
There is little evidence for this view, but there is some support for a genetic predisposition to addiction. Different genes may underlie different addictions: there seems to be a link between tobacco smoking and genes involved in dopamine regulation (Lerman et al) whereas cannabis, cocaine and heroin addiction links to a gene in a different brain system (Comings et al)
Family studies are often carried out to investigate the possibility of genetic transmission. Family studies of alcohol use disorders have shown high rates amongst relatives. Merikangas et al found that 36 per cent of relatives of an individual with an alcohol use disorder were also diagnosed with alcohol use disorder. However, difficult to separate genes and environment in these studies. Adoption studies such as Heath, 2000 support the idea of a genetic contribution to addiction. Twin studies offer additional support for a genetic component (heritability). Heritability of nicotine dependence was found to be between 60 and 70 per cent (Kendler et al) and alcohol dependence at 39 – 60 per cent (Heath et al)
By which mechanism does the genetic influence take effect?
· Biochemical (How addictive substances are metabolised in the brain
· Psychological (how psychological factors such as personality determine behaviour)
· Obviously, even if there is a genetic predisposition, ingestion of the substance is necessary for the individual to become addicted. This probably results from environmental factors.
· This means that legislation and prevention measures are still important even if addiction is genetic – availability of a substance will determine whether the individual becomes addicted.
Two major pathways have been identified in addiction
· The dopamine reward system: the mesolimbic dopamine system has been found to be most important for the motivational process. In normal dopamine activity, cells in the MDS are spontaneously active, releasing small amounts of dopamine to the synaptic cleft. May be responsible for maintaining stable mood states. Altman et al found both nicotine and alcohol alter the nervous system by increasing dopamine levels. Also, it has been suggested that those more susceptible to addictions have a more sensitive mesolimbic dopamine pathway (liebman and cooper)