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Addiction to tobacco

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... acetylcholine receptors in the Ventral Tegmental Area (VTA) of the mid brain ... Ventral tegmental area. 12. Drug actions on the mesolimbic pathway. 13 ... – PowerPoint PPT presentation

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Title: Addiction to tobacco


1
Addiction to tobacco
  • Robert West
  • University College London
  • November 2007
  • www.rjwest.co.uk

2
Outline
  • What is addiction?
  • What is tobacco addiction?
  • What are the mechanisms underlying tobacco
    addiction?
  • What does this mean for overcoming tobacco
    addiction?

3
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

4
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

5
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

6
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)

7
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

8
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

9
Cigarette addiction in the UK
www.smokinginengland.info
10
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

11
Mesolimbic dopamine pathway
Nucleus accumbens
Ventral tegmental area
12
Drug actions on the mesolimbic pathway
13
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

14
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

15
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
16
Mechanisms of nicotine addiction 4 Weakened
impulse control
  • After repeated nicotine exposure, there may be a
    reduction in the ability to inhibit responses

17
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
18
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

19
Additional reading
  • West R and Shiffman S (2007) Smoking Cessation.
    Healthcare Press, Oxford

20
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
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