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 Anticipated pleasure/ satisfaction Desire to smoke Need to smoke 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 Anticipated praise Desire not to smoke Need not to smoke 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