The Biology of Addiction:

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The Biology of Addiction

• The Brains Role

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The Brain

• Transforms environmental stimulation into
  electrical impulses for the mind to interpret
• Types of brain cells
• Glial cells support cells ? provide
  nourishment and insulation
• Neurons working cells ? generate and transmit
  electrical impulses

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Parts of Neuron

• Cell body life support centre
• Nucleus control centre
• Dendrites fingers receiving incoming signals
  from other neurons
• Myelin Sheath fatty membrane surrounding the
  axon
• Axon terminal buttons generating, storing,
  and transporting signals to other neurons
• Neurotransmitters chemical substances that
  transmit electrical impulses across a synapse.

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Neurotransmitters most involvedin addiction

• Dopamine ? master molecule
• increase sense of pleasure
• Related to
• Motor control
• Processing information
• Abstract thinking
• Excitement

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• Serotonin ?
• Related to
• Mood regulation
• Emotionality
• Appetite
• Sleep patterns
• Sociability

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• Endorphin ? secondary feel-good chemical
• Works with dopamine to increase pleasure
• Related to
• Relief of pain
• Sense of well-being

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How drugs affect neurotransmitters

• Cocaine blocks the re-uptake of dopamine ? this
  keeps the pleasure circuit firing ? burst of
  energy/insight/alertness
• Amphetamines block re-uptake and increase the
  production of dopamine ? powerful feeling of
  euphoria/stamina
• Heroin increases dopamine and endorphin ? intense
  rush followed by dream-like state
• Alcohol increases level of all neurotransmitters
  (including GABA) ? at first feel sociable,
  disinhibited, and then later sleepy

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Chemical Tolerance

• Chronic use of any drug reduces the number of
  dopamine producers and receivers. Thus pleasure
  circuit calms down and requires higher levels of
  drug to get high
• Less efficient pleasure circuit also means
  feelings of depression occur when drug not
  present
• Abstinence allows dopamine receptors to
  eventually return to normal

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Chemical Imbalances

• Certain individuals are born with an imbalance of
  neurotransmitters, making them genetically
  predisposed to addiction
• These persons often exhibit attention problems
  and sleep disorders (and sometimes, general
  antisociality) during childhood
• People who compulsively seek novelty also tend to
  abuse drugs ? novelty seeking seems to be genetic

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Genetic Contributions to Addiction

• Points to remember
• Parents pass on both genes and experience
• Genes influence absorption, metabolism,
  excretion, receptor sensitivity, etc.
• Psychologists make certain assumptions on the
  basis of adoption studies

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Early Findings (prior to 1990)

• 1/3 of alcohol abusers have at least one parent
  who is alcoholic
• Children of alcoholics show increased risk of
  developing alcoholism even when adopted at birth
  by non-alcoholic parents
• Those with alcoholic parents have an earlier
  onset of abuse, increased severity of symptoms,
  and greater number of legal and medical
  complications attributable to abuse

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More recent research (1995)

• Sons of alcoholics have reduced sensitivity to
  alcohol. Those most insensitive were most likely
  to be diagnosed as alcohol dependent
• Presence of tolerance seems to predict the
  development of alcoholism even in subjects
  without a family history of alcoholism
• May cause physical dependence to precede
  psychological dependence

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• Identification of the gene for alcoholism ?
  discovery made by postmortem results
• The opposite influence can also be inherited ?
  less effective metabolizing ? facial flushing ?
  probability of becoming alcohol dependent is
  reduced