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Flashcards in Addiction: Biological Explanation Deck (23):

What are the Biological Explanations of Addiction?

1. The Role of Dopamine
2. Genetic Factor


Describe the Mesolmibic (Reward) Pathway.

- Evolved in humans to be adapted response to behaviors that are good for us e.g. eating
- Release of dopamine can be triggered by behavior (e.g. gambling) or a substance (e.g. alcohol)

Addictive Behavior/Substance
| Release of Dopamine
Vental Tegmental Area (VTA)
| Sense of Pleasure
Nucleus Accumbens (NAC)


Why is Tolerance Experienced?

- Dopamine receptors become less sensitive
- Causes a decrease in D2 receptors = decrease in dopamine released


Explain the Correlation Between Tolerance and Withdrawal

- Addict will need to engage in more addiction to experience same effects + avoid withdrawal symptoms
- Engaging in behavior becomes more about avoiding withdrawal symptoms rather than experiencing initial pleasure


What Role does the Frontal Cortex Play in Maintaining the Addiction?

- Linked higher cognitive functions (e.g. decision making + memory)
- Addictive behavior changes brain circuits that decide what to pay attention to - too much importance (salience) to behaviors/cues associated with addiction.
- Dopamine system makes individual want to engage in behavior rather than like it - many addicts report that they no longer enjoy the experience but cannot overcome the cravings.


What has Research Found Regarding to the Role of the Frontal Cortex and Maintaining the Addiction?

- Research evidence with cocaine addicts
- Volkow = abnormalities in frontal cortex
- Bolla = impaired performance frontal cortex task
- Wang = increase activity in frontal cortex when exposed to addictive behavior.


The Role of Dopamine Evaluation
Not All Addictive Behaviors

- Evidence to show that dopamine increase following drug consumption is not always the case
- Stokes (2009) = No significant increase in cannabis users
- Yoder (2007) = No consistent increase in dopamine when given alcohol
- Not appropriate to say that dopamine explains all addiction


The Role of Dopamine Evaluation
The Complexity of the Role of Dopamine

- Dopamine has a range of other functions
- Bell (2013) = dopamine is the Kim Kardasion of Neurotransmitters - fashionable to blame dopamine for causing a range of problems
- Dopamine levels increase in presence of aversive stimuli - helps us to avoid situations
Liberzon (1999) = increased activation in NAC in veterans suffering from PTSD when reminded of battles through combat sounds
- Doesn't match the idea of this area being simply about pleasure


The Role of Dopamine Evaluation
Methodology Issues

- Nutt (2015) = criticized the methodology used by researchers in this area
- Samples were small + participants given substance to measure its effects - often in a different form
- Given in a lab rather than usual environment
- measured effects are not always accurate


The Role of Dopamine Evaluation
Use of Non-Human Animal Studies

- Studies may not give true insight into how humans become addicted
- Misses social context in which addictions take place - cannot replicate same behaviors of addiction
- However, does allow researcher to study the effects of drugs in ways that aren't possible with humans


How is the Role of Dopamine Applied to modify addiction? (Using Varenicline)

- Addiction linked to the pleasure an individual feels as a result of dopamine being released
- By reducing the dopamine being released could hep to diminish cravings for the addictive behavior
- Varenicline (champix) is a prescribed drug to help people stop smoking
- Varenicline binds to nicotine receptors, tricking brain into thinking it's had nicotine - leads to a small release of dopamine
- Also reduces rewarding effects of nicotine by blocking nicotine's ability to access the receptor + activate release - if person smokes a cigarette person will get pleasure from it
- Drug has proved the be successful - provide extra support for the role of dopamine in addiction - However most effective when used alongside other methods.


What Genes are Associated with Addictions?

1. DRD2
2. ADH Gene


What does DRD2 mean?

- D2 Dopamine Receptor Gene


How is DRD2 Associated with Addictions?

- Individuals with A1 varient of gene have fewer dopamine receptors in the area of the brain which provides us with sense of pleasure to normal adaptive behavior (e.g. sex + food)
- lower numbers of dopamine receptors leads individual to compensate for this over stimulation through engaging in addictive behavior
- Comings (1996) = 48.7% smokers carried A1 variant compared with 25.9% of general population
- Gambling Addictions = 50.9% of addicts carried A1 variant compared with 25.9% of non-addicts.


What does ADH and ALDH mean?

- ADH = Alcohol Dehydrogenase
- ALDH = Acetaldehyde Dehydrogenase


Describe the Breakdown of Alcohol

| Broken down by ADH
| Broken down by ALDH
/ \
/ \
Acelic Acid Water


How is ADH Associated with Addictions?

- Some variants of ALDH + ADH gene decreases risk of alcoholism by increasing acetaldehyde - causes unpleasant reactions to alcohol (e.g. Nausea)
- Mainly found in East Asians populations - help to explain lower rates of alcoholism in these cultures
- Variants of ADH may break down alcohol at a slower rate - likely to drink more + become addicted


What was the Diathesis- Stress Model?

- Suggests that addictions occur when a genetic predisposition to the disorder is triggered by an environmental stressor.


Genetic Factor Evaluation
Difference Between Imitation + Maintenance

- Twin studies used to demonstrate the influence of genetic factors in addiction
- Kendler + Prescott = interviewed 2000 twins - found social + environmental factors influence a person's cocaine use - however whether person becomes addicted more dependent on genetic factor
- Concordance rates for cocaine initiation -
MZ= 54% DZ=42%
- Concordance rates with cocaine dependence -
MZ = 35% DZ=0%


Genetic Factor Evaluation
Genes for Addiction?

- Relationship between genetics + addiction is very complex
- Ojelade (2015) = RSU1 not functioning properly in fruit flies - lower sensitivity to alcohol
- Brain imaging used in humans to test for this - found a relationship between this and alcohol dependency
- The range of different genes identified means we cannot say that there is one gene for addiction
- Number of different types of addictive behaviors all of which may be triggered by different genetic mechanism


Genetic Factor Evaluation
Social + Cultural Factors

- Kendler (2000) = heritabelity of tobacco changes over time
- Kendler completed a twin pair study between 1910-1958 - found that women born in the 1st 1/2 had little/no influence on the heriability - women born in the 2nd 1/2 had a heriability of 60%
- Boardman (2008) = twin + sibling study found a strong genetic component in smoking behaviors the rate for daily smoking varied across schools
- Herilability rate was highest in schools where the most poplar students smoke


Genetic Factor Evaluation

- Only some people are likely to addictive
- Reduces amount of blame placed on addict - suggesting that they could not have controlled addiciton
- Individual sees addiction as an unstoppable consequence of their genetic makeup - less likely to take responsibility for their own recovery


Genetic Factor Evaluation
Rejection of Disease

- Lewis (2015) = labeling addiction as a disease can damage addicts self essteam and make them feel helpless in overcoming their addiction
- Lewis also suggests to consider changes that happen in the brain as a form of learning