Addiction to tobacco

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Addiction to tobacco

• Robert West
• University College London
• November 2007
• www.rjwest.co.uk

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Outline

• What is addiction?
• What is tobacco addiction?
• What are the mechanisms underlying tobacco
  addiction?
• What does this mean for overcoming tobacco
  addiction?

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Addiction

• Addiction is a chronic disposition to experience
  such powerful motivation to engage in a
  reward-seeking activity, and/or a weakened
  disposition to inhibit that activity, that it is
  maladaptive
• An addiction is a reward-seeking activity that is
  chronically given such a high priority that it is
  maladaptive
• An individual is addicted to an activity to the
  extent that he or she gives it such a high
  priority that it is maladaptive
• An activity is addictive to the extent that it is
  addictive to a large proportion of a population

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Other definitions

• Addiction is a condition in which there is
  impaired control over a reward-seeking activity
• Addiction to an activity means that is needs to
  be repeated to stave off adverse withdrawal
  symptoms
• Addiction is a drug-seeking behaviour that occurs
  at a high rate and is maladaptive
• Addiction is an activity to which an individual
  has become excessively attached

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What is wrong with these definitions

• Someone can still be addicted even if he or she
  has never sought to exercise control over an
  activity
• Someone can still be addicted even if he or she
  is currently able to exercise control over an
  activity
• People can be addicted to activities other than
  drug taking
• Relapse to an addiction often occurs in the
  absence of withdrawal symptoms
• Addiction does not just involve attachment

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The role of withdrawal symptoms

• Withdrawal symptoms may still play a major role
  in some addictions
• by being a powerful direct source of motivation
  to engage in the activity
• by leading the addict to be motivated to engage
  in the activity when similar symptoms are present
  even though they arise from another source
  (because of over-generalisation)

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Main signs and symptoms of tobacco addiction

• High rate of use of the tobacco product
• High levels of nicotine in the body
• Using the product first thing on waking or even
  during the night
• Continuing to use tobacco products despite
  wanting to stop
• Failing in attempts to stop using tobacco
  products
• Experiencing powerful wants, needs or urges to
  use tobacco in situations when smoking would
  normally occur

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Tobacco, cigarettes and nicotine

• Tobacco is addictive because it delivers nicotine
  into the body
• Different forms of tobacco probably have
  different degrees of addictive potential
• Cigarettes are probably the most addictive form
  and this is probably because
• they deliver nicotine very rapidly to the brain
  in easily adjustable concentrations
• the nicotine hit is directly associated with
  the activity of smoking
• they provide other rewards which nicotine
  potentiates
• Slow release nicotine products such as the
  transdermal patch are minimally addictive

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Cigarette addiction in the UK
www.smokinginengland.info
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Mechanisms of tobacco addiction 1 Nicotine reward

• When nicotine is absorbed it attaches to
  nicotinic acetylcholine receptors in the Ventral
  Tegmental Area (VTA) of the mid brain
• This stimulates firing of neurons that project
  forward to the Nucleus Accumbens (NAcc)
• This causes dopamine release in the NAcc
• This acts as a reward and creates impulses to
  smoke when cues to smoking are present
• It is not clear whether the smoker needs to feel
  enjoyment or whether the process can operate
  outside any conscious awareness of reward

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Mesolimbic dopamine pathway
Nucleus accumbens
Ventral tegmental area
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Drug actions on the mesolimbic pathway
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Mechanisms of nicotine addiction 2 Acquired drive

• In many smokers, after repeated ingestion of
  nicotine, the motivational system is altered to
  create a drive a hunger for cigarettes
• The drive increases in the minutes to hours since
  the last cigarette and is influenced by triggers,
  reminders, stress and distractions
• The drive is experienced as a need to smoke
• The drive usually dissipates over weeks of not
  smoking
• The drive could be caused by abnormally low
  levels of firing in the pathways projecting from
  the VTA

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Mechanisms of nicotine addiction 3 Withdrawal
symptoms

• After repeated nicotine exposure, abstinence
  results in unpleasant withdrawal symptoms
  including
• depression
• anger
• restlessness
• hunger
• difficulty concentrating
• Smoking relieves these symptoms
• Overgeneralisation of this effect means that
  adverse mood and physical symptoms, however
  caused, come to generate a need to smoke

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Motivation to smoke
Smoking
Impulse to smoke
Cues/triggers
Desire to smoke
Need to smoke
Anticipated pleasure/ satisfaction
Nicotine hunger
Unpleasant mood and physical symptoms
Anticipated benefit
Reminders
Positive evaluations of smoking
Smoker identity
Beliefs about benefits of smoking
Plan to smoke
Nicotine dependence involves generation of
acquired drive, withdrawal symptoms, and direct
simulation of impulses through habit learning
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Mechanisms of nicotine addiction 4 Weakened
impulse control

• After repeated nicotine exposure, there may be a
  reduction in the ability to inhibit responses

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Inhibition of smoking
Not smoking
Inhibition
Cues/triggers
Desire not to smoke
Need not to smoke
Anticipated praise
Anticipated disgust, guilt or shame Fears about
health
Anticipated self-respect
Positive evaluations of not smoking negative
evaluations of smoking
Reminders
Beliefs about benefits of not smoking
Non-smoker identity
Plan not to smoke
Nicotine dependence probably also involves
impairment of impulse control mechanisms
undermining response inhibition
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Implications for overcoming tobacco addiction

• Reduce need to smoke in first few weeks with
• agonist and substitution therapy (NRT, Zyban,
  Champix, nortriptyline)
• avoiding reminders and use distraction
• minimising external stressors
• using exercise and psychological techniques to
  maintain activity in pathways from VTA
• Reduce rewarding effect of smoking with
  antagonist therapy
• Minimise impulses to smoke by avoiding triggers,
  especially availability of cigarettes
• Generate competing wants and needs including
  identity change

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Additional reading

• West R and Shiffman S (2007) Smoking Cessation.
  Healthcare Press, Oxford

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Conclusions

• Addiction involves powerful wants, needs and
  impulses to engage in an activity and/or lowered
  capacity or motivation to desist
• Cigarettes are highly addictive as evidenced
  largely by the very low probability of success of
  even strenuous quit attempts
• This is because they deliver nicotine, but not
  all nicotine products are equally addictive
• There are four putative mechanisms
• nicotine reward setting up the impulse to smoke
  in response to triggers
• an acquired drive resulting from chronic exposure
  to rapid nicotine hits
• withdrawal symptoms from which smokers
  overgeneralise
• reduced capacity to inhibit responding caused by
  nicotine withdrawal
• Combating tobacco addiction involves targeting as
  many levels of the motivational system as
  possible with pharmacological, psychological,
  social and environmental interventions