Biological model of addiction

Main assumptions of the biological model (3)

- Addiction is an illness in the individual - It is irreversible - Needs to be medically treated.

How does the disease model explain the maintenance of addiction (4)

- Chronic exposure to the addiction results in a reduction in the activity of the positive reward circuits in the brain (known as down-regulation). - This generates a stressful situation for the addict characterised by withdrawal symptoms, sadness and anxiety. This negative state becomes the dominant force driving the drug craving. - The user no longer takes drugs to obtain a pleasurable experience (positive reinforcement) but takes them to avoid an unpleasurable state (negative reinforcement). - As a result of down regulation the drug levels needed to trigger the brain reward system increase.

How does the disease model explain the relapse of addiction (3)

- Desire for the drug may assume more importance than most other desires. - Despite the drug no longer giving much if any pleasure the brain still receives difficult to resist signals of imminent reward that force the addict to take the drug again. - These changes do not make addiction inevitable but permanent recovery is made more difficult due to the lasting memories of the drug through the drug induced changes.

How does the disease model explain the initiation, of addiction (4)

- Drug taking produces a rewarding feeling due to the neurotransmitter dopamine in the brain being released. - This then produces lasting memories encouraging the person to do it again. - For example crack cocaine causes a massive and rapid activation of dopamine receptors in the mesolimbic pathway. - This circuit registers the value of important experiences, thereby creating lasting memories that link the drug to a pleasurable reward.

Outline research into genetics (2)

- Family and twin studies are used to research this theory of addiction by looking at genes and medical histories of families. - McGue (1999) found that family and twin studies demonstrated that genes contribute to the development of alcohol dependence in between 50% and 60% of men and women.

Outline the neurobiological approach of addiction (1)

- In this approach the neurotransmitter dopamine plays a major role in addiction. Increased levels of dopamine are associated with pleasure.

How does the genetics view explain the initiation and maintenance of addiction (2)

- It is considered that some people are more likely to take up an addictive behaviour due to their genetic disposition causing initiation and the maintenance due to their genetics. - It may be that people who are sensitive to addiction have inherited a more sensitive mesolimbic dopamine pathway or from a variant of the dopamine receptor D2.

Outline the dopamine and reward pathways (4)

- The Mesocorticolimbic dopamine pathway - This neural pathway is involved in the pleasure and reinforcement associated with natural reward states (such as eating, mating and maternal behaviour). - VTA - A key part of the brain's reward system is the pathway extending from dopamine-producing neurons in the ventral tegmental area (VTA) - NA - Dopamine-sensitive neurons in the nucleus acumbens (NA). - There are also pathways linking the VTA and NA with other brain regions that can help make addicts sensitive to reminders of past highs (such as places where they scored vulnerable to relapse when stressed and unable to control the urge to seek drugs.

How does the neurobiological approach explain relapse of addiction (4)

- The PFC which is involved in decision-making and the inhibition of risky behaviours is impaired in addicts, allowing them to choose immediate rewards even in the face of long term negative consequences. - Continued over-production of dopamine leads to desensitisation in receptors to compensate. - This leads to increased desire to engage in the addictive behaviour to return to the same level of dopamine high (the person is becoming tolerant). - Long term exposure to the addictive behaviour can lead to reduction in the reward pathway activity (down regulation). This results in withdrawal symptoms a cue for relapse.

How does the neurobiological approach explain maintenance of addiction (4)

- The VTA-NA pathway acts as a 'rheostat of reward' i.e. it tells other brain centres how rewarding an activity is. The more rewarding, the more likely the organism is to remember it and repeat it. - The Mesocorticolimbic dopamine pathway - This neural pathway is involved in the pleasure and reinforcement associated with natural reward states (such as eating, mating and maternal behaviour). - VTA - A key part of the brain's reward system is the pathway extending from dopamine-producing neurons in the ventral tegmental area (VTA) - NA - Dopamine-sensitive neurons in the nucleus acumbens (NA). There are also pathways linking the VTA and NA with other brain regions that can help make addicts sensitive to reminders of past highs (such as places where they scored vulnerable to relapse when stressed and unable to control the urge to seek drugs.

Outline disease model view (1)

- The theory is based on addictive behaviours are developed and maintained through reward systems in the brain through dopamine.

How does the neurobiological approach explain initiation of addiction (4)

- This desire for the rewarding pleasurable feeling may account for the initiation and maintenance of addictive behaviour. - Rewarding experiences, such as drug taking, trigger the release of dopamine and effectively telling the brain to do it again maintaining the habit. - The mesocorticolimbic reward pathway is responsible for making sure that addictive behaviour is repeated (maintenance). - This is done via connections to the regions of the brain that control memory and behaviour.

How does the genetics view explain the relapse of addiction (1)

- This idea of genetic vulnerability to addictions may explain why some people are more resistant to treatment and more likely to relapse.

Outline genetics view (2)

- This theory is based on addiction forming through genetics that individuals possess that make them more vulnerable to addiction. - Genes, a variant of the gene DRD2 (dopamine receptor D2) has been found to be linked in 42% of people with alcoholism, 50% of pathological gamblers, 45% of people with Tourette's syndrome and 55% of people who have autism.

Outline support for the genetics view (1)

1. Individual differences - Genetic explanations can explain why some people become addicted yet others who have the same environmental factors do not. Some people are more vulnerable to develop an addiction because of our genetic disposition. This idea of genetic disposition may also explain why some people are more resistant to treatment for the addictive behaviours and are more likely to relapse.

Outline criticisms for the neurobiological approach (2)

1. Methodological problems - Difficulty to infer causality from post mortem studies of human addicts. 2. Reductionist approach - Ignores social factors

Outline criticism for the genetics view (2)

1. Reductionist - Ignores social context making it highly reductionist. 2. DRD2 gene - This gene is said to occur in alcoholics and pathological gamblers as well as individuals who have Tourette's syndrome and autism. This poses a problem for the idea that DRD2 is a 'reward' gene because individuals with Tourette's syndrome and autism are not thought to be particularly 'pleasure seeking'.

Outline criticism for the disease model (1)

1. Reductionist - This biological explanation only takes into account the nature debate meaning nurture is not accounted for. - This means factors such as social influence and the environment are not accounted for unlike the cognitive and learning models associated with addiction.

Outline support for the neurobiological approach (1)

1. Substantial empirical support - Considerable research evidence to support the role of various brain structures and pathways in addictive behaviour.

Outline support for the disease model (1+4)

1. Volkow et al - Gave Ritalin, which gently lifts dopamine levels to a group of adult volunteers. - Some participants loved the feeling of the drug but others hated the way it made them feel. - They then produced scans of their brains and found that those who liked the rush from the drug had fewer dopamine D2 receptors than those who hated it. - Concluding that some people are particularly vulnerable to the added rush given by dopamine-enhancing drugs.