Addiction- Biological explanations Flashcards
What are the 2 biological explanations for addiction?
1) The role of dopamine
2) Addiction genes
What is my first choice for the biological explanations for addiction?
The role of dopamine
What are the 3 aspects to the role of dopamine?
1- The mesolimbic pathway
2- Tolerance and withdrawal
3- Maintaining addiction
Key points about the mesolimbic pathway
The reward pathway
- whenever we engage in addictive behaviours the pathway is activated
- creates a pleasurable feeling which reinforces the behaviour
- drugs also reward centres to activate
- pleasurable feedback is at the very heart of addiction
The mesolimbic pathway
NACs and VTAs
The nucleus accumbens travel from the VTA to NAC where a jolt of pleasure is felt
Ventral Tegmental Area
- dopamine is released from here
Research support for the mesolimbic pathway
Joutsa et al and Boileau
J- D levels were increased in Ps who were given a gambling task, regardless of whether the outcome was a win or not
B- alcohol increased D levels in the brain
What does research from Joutsa and Boileau suggest about the mesolimbic pathway?
Addictive substances and behaviours trigger the release of dopamine in the mesolimbic system
2- How is tolerance created
The brain adapts in response to experience and will strive to reach equilibrium, balance//stability
- if a drug is consumed regularly, it will alter the function of the brain as we upset the balance
- the brain will adapt to minimise the effect of the drug and restore normal function
- a higher and higher dose will be needed to achieve the same effect
2- How is withdrawal created?
If a drug is used regularly, the brain compensates and adapts to maintain balance whilst the drug is present undergoing a process of neuroadaptation
- when the drug is no longer being taken, the brain becomes out of balance
- it can take neuroadaptation a long time to adapt to the absence of a drug
- causes the symptoms of withdrawal
Why do people take drugs when experiencing withdrawal?
The unpleasant side effects
- now no longer being taken for its pleasurable effects, but rather to avoid the withdrawal symptoms
Tolerance and nuerotransmitters
Tolerance works at the level of NTs with D2 receptors
- different receptors are compatible with different NTs
- D2 receptors are a specific type of NT that dopamine attaches itself to
What did Volkow et al find in relation to tolerance and withdrawal?
Found that in users of cocaine, there was a reduction in both the number of d2 receptors in the brain, as well as a reduction in the release of dopamine
- brain removes D2 receptors so that less dopamine can bind to it
3- Maintaining addiction
What are the responsibilities of the frontal cortex?
- impulse control
- problem solving
- motivation
- social behaviour
- judgement
- decision making
These all help to maintain addiction
How does the frontal cortex help to maintain addiction?
Human brains are complex, and a simple pleasure response is not enough to explain all of the characteristics of addiction
evidence- the fact that when the drug is no longer being taken, and the negative effects of withdrawal and tolerance have disappeared, relapse can still occur
How does Volkow et al’s research support the argument on the maintenance of addiction?
Cocaine addicts show abnormalities in their frontal cortex
How does Wang et al’s research support the argument on the maintenance of addiction?
Addicts show an increase in activity in their frontal cortex when exposed again to the drugs or cues associated with them
How does Robinson’s and Berridge’s research support the argument for the maintenance of addiction?
Dopamine system plays the role of making the individual want to engage in the behaviour rather than imply making them like i
- why addicts report they no longer enjoy the experience, cannot overcome ravings associated with it
Evaluation: The role of Dopamine
X Methodology
NUTT- small samples of the substance to measure the effects
- given in different forms such as nicotine inhalers
- lab environment lowers ecological validity and accuracy of the measured effects
X cannot imitate a social group, social smokers
Evaluation: The role of Dopamine
- Research support
Wang et al
- increased activity in frontal cortex, exposed again to drug or cue associated, evidence of behavioural effect
X LIBERZON- war veterans, combat sounds
x avoid something unpleasant
x not just to seek out pleasure
Evaluation: The role of Dopamine
- Applications
- reduce social stigma
- addiction seen as disease to be treated
- addicts may be more supported to seek and receive help
- treated rather tan punished
X limits accountability
X changes to frontal cortex
X helplessness
What is the second biological explanation and also SECOND choice?
Addiction genes
What does addiction genes suggest?
- NTs like dopamine are involved in addiction, doesn’t explain why many people engage in behaviours but do not become addicted
- genes explain responses to types of behaviour
- variations of genetic makeup
- increase of decrease susceptibility
How can we used inheritance studies to back up addiction genes?
Investigate the role that genes play in addiction and how this varies in family, twin studies
What are the 4 key parts of addiction genes?
1- Inheritance studies
2- DRD2
3- ADH
4- Diathesis stress model
1- How does Prescott and Kendler’s research show about addiction genes?
Personal interviews to assess alcohol abuse and dependence amongst twins
- male-male pairs
- concordance rates were much higher in MZ twins when compared to DZ twins
48-58% of the variance in alcohol in addiction is genetic
What can we conclude from Prescott and Kendler’s research on twins?
Indicates that there could be a genetic basis for addiction but environmental factors may also play a role
Genes associated with addiction
Some people carry gee=ne that make them more prone to developing an addiction- consuming a potentially addiction substance/engaging in a behaviour
What gene makes you less likely to become addicted?
ADH
What gene makes you more likely to become addicted?
DRD2
DRD2
A dopamine gene
- individual with the a1 variation have fewer dopamine receptors (D2)
What does the DRD2 gene do?
Codes for the amount of dopamine receptor sites
What does the DRD2 variant A1 cause to happen?
Fewer dopamine receptor sites
What effect does the A1 variant have on behaviour?
This lower number means that they try and compensate for this by overstimulation through engaging in addictive behaviour
What did Comings et al do and find?
Found that 48.7% of smokers and ex-smokers carried the A1 variant of the DRD2 gene compared with 25.9% of the general population
What does Coming et al’s research suggest about the role of the A1 gene?
Suggests that the A1 gene impacts the likelihood of addiction as it reduces D2 sites leading to overstimulation, encouraging addictive behaviour
What are the ADH and ADLH genes responsible for?
How alcohol is metabolised
- broken down and eliminated by the body
What do ADH and ADLH genes do?
ADH- fast, toxic effect quickly
ADLH- slow, long time to process
Why do certain variants of these genes decrease the risk of alcoholism?
The effects are so unpleasant that thy do not want to do it again
How is this supported by alcohol rates in East Asian populations?
Their culture does not drink, lots of people have the unpleasant effects so choose not to drink
How do other variants of this gene increase the risk of alcoholism?
ADH- slow, do not get the toxic, unpleasant effect
ADLH- fast, all at once, broken down quicker o the do not feel it
4- What is the diathesis stress model?
Genetic risk, environmental trigger
What are the main ideas of the diathesis stress model?
It is too simplistic to suggest that addiction could be caused by just genetics
- consider how genetics interact with the environment
- a disorder such as addiction only develops when a predisposition to the disorder is triggered by an environmental stressor
Evaluation: The role of genetics
X Methodology
1X users will engage in multiple drug use
- difficult to investigate trends
2X come in and out of fashion so vary in availability
- no opportunity to investigate genetic basis
3X only focus on drugs or alcohol
- behavioural addiction understudied
Evaluation: The role of genetics
- Research support
Prescott and Kendler
- higher concordance rate in mx twins
48-58% variance in alcohol is genetic
X share the same environment
X rates aren’t 100%m must be another factor
Evaluation: The role of genetics
X- Social and ethical implications
E- reduce risk of developing addiction, seek support
X be paranoid, forced to get vaccine or join prevention programme
X determinism and free will
CJS- rule more sympathetically or deemed guilty if they have low addictive potential`
