Biological explanations of addiction

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  • Created by: stef16
  • Created on: 08-02-16 14:28
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  • Biological explanations of addiction
    • Maintenance
      • Receptors
        • Withdrawal symptoms start to occur
        • Become less sensitive
        • Dysphoric state
      • Down regulation
        • Chronic overexposure to addictive substances eventually leads to a reduction in activity of positive circuits
      • Actual drug taking increases
      • Reinforcement
        • Not for pleasure (positive reinforcement) anymore
        • Maintained in order to avoid unpleasant state (negative reinforcement)
    • Evaluation
      • Social context
        • People who lead stressful lives more prone to addiction
        • Losing social status means a loss of DR2 receptors
      • Reductionist
      • Individual differences
        • Shown by Ritalin study on children, Volkow et al.
      • Shows importance of biological and physiological processes
        • Addiction caused by malfunction of reward pathways - partly
        • Nalextrone and sex addiction
          • Stopped dopamine release, behaviour no longer gave reward so it went extinct
    • Genetics
      • Kendler et al. - hereditability of nicotine addiction dependence - 60-70%
      • DRD2
        • Alcoholism
          • A1 variant found in 2/3 deceased alcoholics, 1/5 of alcoholics had this variant
          • Blum et al. - increased prevalence of A1 among children born to alcoholics - genetic link
        • Smokers
          • Men with A1 variant started smoking earlier and abstain for shorter periods
          • 48.7.7% of smokers had A1 variant compared to 25.9% of non-smokers
    • Initiation
      • Range of pressures e.g. social, biological
      • Positive reward pathway
        • excitement of gambling can result in release of adrenaline, this energy boost can be addictive
      • Genetics
        • Those with D2A1 more likely to become gamblers
        • Those with SLC6A3-9 gene less likely to smoke
    • Disease model
      • Addiction is an illness
        • Treatment and prevention
      • Emphasis on treatment
        • Though it is irreversible due to brain chemistry changes
    • Relapse
      • Frontal cortex less effective at decision making
      • Need for drug greater than anything else
      • Brain tries to force behaviour due to lasting pleasure memories
      • Addict that is abstaining constantly sees cues
        • Constant reminder and stimulates dopamine in expectation of reward - even if it won't come
      • Animal studies
        • Mice lacking a particular receptor don't become cocaine addicts
        • PET scans on primates exposed to amphetamines - reduced D2 density
        • Monkey cocaine addiction - sub for less addictive substance which mimics. Effective. Replicated on humans
        • Exercise in speculation? Hackman & Redelmeier
    • Dopamine
      • Mesolimbic dopamine system
        • Spontaneous release of dopamine, maintaining regular mood
        • Suggested people with more sensitive MDS are more susceptible to addiction. Liebman and Cooper
        • Crack stimulates massive activation of the mesolimbic pathway
      • Regulates mood and emotion. Heavily involved in motivation and reward processors
      • Both alcohol and nicotine affect NS by increasing dopamine levels
      • Incentive sensitisation theory
        • Repeated exposure to drugs increases body's need for them

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