Measuring craving in a clinical setting

1. Measuring craving in a clinical setting Robert West University College London Madrid October 2007

2. Outline • ‘Craving’ and ‘subjective motivation to smoke’ (SMS) • Why measure SMS? • How to evaluate a measure of SMS • Existing measures of SMS • Comparative evaluation of these measures • Conclusions

3. Simple truisms • Smoking a cigarette after the target quit date results from the fact that, on an occasion when a cigarette is available, the motivation to smoke is stronger than the motivation to resist • Motivation to smoke when cigarettes are not immediately available can also drive behaviour to obtain them

4. Terms relating to motivation • Motivation • mental activity that energises and directs behaviour: encompasses conscious deliberation as well as habitual and instinctive reactions • Desire • feeling of wanting or needing something • Urge • feeling of being impelled to engage immediately in a particular action • Craving • ???

5. Craving: lay definitions • ‘A consuming desire; yearning’ • (www.thefreedictionary.com) • ‘An intense desire for some particular thing’ (www.wordnet.princeton.edu) • ‘an intense and prolonged desire; yearning or appetite, as for affection or a food or drug’ (www.yourdictionary.com)

6. Craving: academic definitions • Expectancies about positive outcomes or escape from or avoidance of negative outcomes • Feelings of urges arising out of frustration of automatic impulses • Need to escape from unpleasant withdrawal symptoms • Physiological changes during abstinence

7. Kozlowski was right; I was wrong • 1987: Use and misuse of the concept of craving by alcohol, tobacco, and drug researchers’, Br J of Addiction, 82, 31-45 • The concept is used by academics ambiguously and to mean different things • 1989: "Cravings" are ambiguous: ask about urges or desires, Addictive Behaviors, 14, 443-445 • ‘Despite the dictionary definition of "craving" (a strong desire), two studies indicate that a substantial percentage of persons with alcohol and drug problems use the word "craving" to mean any desire or urge, even a weak one, to use substances. Researchers and clinicians are advised to beware of this ambiguity of "craving" and to consider the conceptual status of "craving" in their work.’

8. Problems with the term craving • Academic definitions are proposed without establishing that they are more useful than the lay definition • Varying definitions are used • Measures based on one definition are interpreted as though they measured another definition • Most of the motivational theory underpinning the definitions is implicit and imprecise or explicit but only captures some aspects of motivation • The Questionnaire on Smoking Urges (QSU) which is based on a particular non-lay definition is becoming a de facto standard even though it has not been evaluated against existing measures

9. Addressing the problem • Use the term ‘subjective motivation’ to refer to the broad experience of motivation to engage in a particular activity and Subjective Motivation to Smoke (SMS) • Use the term ‘craving’ when the measurement focuses on intense desire as in the lay definition

10. Broad strategy • Evaluate the existing measures of SMS, using a range of indices of validity • Adopt a parsimonious approach, staying with simple measures unless more complex measures are shown to be necessary • Note: SMS relies on introspection and therefore can only assess aspects of motivation to smoke that can be experienced and reported using a common language

11. Why measure SMS in clinical settings? • Clinical research • as a proxy for abstinence in trials aimed at assessing likely effectiveness of cessation aids • in order to determine the mechanism of action of cessation aids • in order to gain a fuller understanding of smoking behaviour and why people find it hard to stop • Clinical practice • to assess prognosis • to provide information on which to adjust treatment and management

12. 5 criteria for evaluating measures of SMS in clinical settings • How sensitive are they to abstinence? • How far do they give consistent results when purportedly measuring the same level of motivation on different occasions? • How sensitive are they to interventions that affect relapse rates? • How well do they predict relapse? • How resource intensive are they?

13. Existing scales • Minnesota Nicotine Withdrawal Scale (MNWS) • Shiffman craving scale (SCS) • Wisconsin Smoking Withdrawal Scale (WSWS) • Cigarette Withdrawal Scale (CWS) • Mood and Physical Symptoms Scale (MPSS) • Questionnaire on Smoking Urges (QSU) • Single rating of craving • Smoker Complaint Scale (Schneider)

14. MNWS (Hughes)

15. Shiffman scale • For each item below, please circle the number (1-10) that shows best how you have felt today. • Urge to smoke • Need to smoke • Crave a cigarette • Need a cigarette

16. WSWS (Welsch)

17. CWS (Etter)

18. MPSS (West) How much of the time have you felt the urge to smoke today? How strong have the urges been today?

19. Brief QSU (Tiffany) 1: I have a desire for a cigarette right now 2:Nothing would be better than smoking a cigarette right now 3: If it were possible I would probably smoke now 4: I could control things better right now if I could smoke 5: All I want right now is a cigarette 6: I have an urge for a cigarette 7: A cigarette would taste good now 8: I would do almost anything for a cigarette now 9: Smoking would make me less depressed 10: I am going to smoke as soon as possible Items in black are Factor 1 and items in blue are Factor 2

20. Craving rating How much have you craved cigarettes today?

21. Study 1: Sensitivity to abstinence • Methods • 60 male and female smokers randomly allocated to ‘abstinence’ versus ‘continue smoking’ conditions (30 in each group) • SMS measures taken at baseline and after 24 hours • checked abstinence with expired air CO • measures were: QSU Factor 1, QSU Factor 2, QSU total, MPSS strength of urges, MPSS time spent with urges, MPSS total, MNWS, Shiffman scale, WSWS, CWS, ‘craving’ rating

22. Subject characteristics Mean (SD) age: 30 yrs (9.8) Mean (SD) cigs per day: 15 (6.1) Mean (SD) reported quit attempts in past 5 years: 1.9 (1.9)

23. Sensitivity to abstinence: analysis • General linear model examining interaction between • time (baselines versus 24 h) and • group (continue smoking versus abstain) • Calculate eta squared (variance accounted for) for each SMS measure • Also calculate eta squared for prediction of 24 h score from baseline score

24. Sensitivity to abstinence: results All values are greater than zero at p<.0001

25. Consistency: analysis • Select smokers who continued smoking • Calculate correlation between 24 h score and baseline score for each measure

26. Consistency: results All values are greater than zero at p<.0001

27. Combining scales • Used forward stepwise logistic regression to assess independent contribution of each scale to distinguishing between the abstinent and non-abstinent smokers • QSU total score and MPSS total score made independent contributions but additional effect of adding one to the other was small

28. Study 2: Sensitivity to medications aiding cessation • Methods • combined data from two phase 3 trials comparing varenicline, bupropion and placebo • 1818 participants provided SMS data one week after the target quit date • examined the effect of varenicline versus bupropion versus placebo on SMS at this time point using baseline measurements as covariates • did this separately in abstinent and non-abstinent participants • used Brief QSU and the single ‘desire/craving’ rating from the MNWS • calculated t-values for pairwise comparisons with adjustment for multiple post-hoc comparison

29. Results t-values provide a comparable estimate of effect size; A=abstinent, NA=non-abstinent

30. Conclusions • The term ‘craving’ is used in varying ways and operationalised differently in different measures • The term ‘subjective motivation to smoke’ (SMS) might be more appropriate in research studies with ‘craving’ being reserved for ‘intense desire’ • In terms of sensitivity to abstinence and consistency, single ratings or scales with two items appear to work as well as the Brief QSU with 10 items • In terms of sensitivity to medications that affect abstinence and are believed to reduce the need to smoke a single rating of ‘desire/craving’ performs the same as the Brief QSU • There seems to be nothing to be gained by using multi-item scales such as the Brief QSU and a range of shorter scales or single item ratings are available for measuring SMS • There may be a small advantage to using the Brief QSU with the MPSS when there is a strong need to maximise precision but this needs to be tested further

31. ‘Better fewer, but better’ V. I. Lenin

32. Thanks • Study 1 was supervised by Dr Michael Ussher at St George’s, University of London • The analysis for Study 2 was undertaken by Joseph Cappelleri and Andrew Bushmakin of Pfizer