Transcript The PRIME Theory of motivation and its application to

Measuring craving in a clinical
setting
Robert West
University College London
Madrid
October 2007
1
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
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
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
– ???
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)
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
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.’
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
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
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
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
5 criteria for evaluating measures
of SMS in clinical settings
1. How sensitive are they to abstinence?
2. How far do they give consistent results
when purportedly measuring the same
level of motivation on different
occasions?
3. How sensitive are they to interventions
that affect relapse rates?
4. How well do they predict relapse?
5. How resource intensive are they?
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)
MNWS (Hughes)
Please show how you have
been feeling today
Desire or craving to smoke
None
Slight
Mild
Moderate
0
1
2
3
Severe
4
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
WSWS (Welsch)
Please show on each of
the scales below how
you have been feeling
today
Strongly
disagree
Disagree
Feel neutral
Agree
Strongly
agree
I have frequent urges
to smoke
0
1
2
3
4
I have been bothered
by the desire to smoke
a cigarette
0
1
2
3
4
I have thought about
smoking a lot
0
1
2
3
4
CWS (Etter)
The following statements
describe how you feel today.
Please indicate how much you
agree or disagree with each of
these statements.
Totally
disagree
Mostly
disagree
More or
less
agree
Mostly
agree
Totally
agree
The only thing I can think
about is smoking a cigarette
1
2
3
4
5
I miss cigarettes terribly
1
2
3
4
5
I feel an irresistible need to
smoke
1
2
3
4
5
MPSS (West)
How much of the time have you felt the urge to smoke today?
A lot of the
time
Some of the
time
A little of the
time
Not at all
All the time
Almost all
the time
5
4
3
2
1
0
How strong have the urges been today?
Extremely
strong
Very strong
Strong
Moderate
Slight
No urges
5
4
3
2
1
0
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
Strongly
disagree
1
Neutral
2
3
4
Strongly
agree
5
Items in black are Factor 1 and items in blue are Factor 2
6
7
Craving rating
How much have you craved cigarettes today?
A great deal
Quite a bit
Somewhat
A little
Hardly at all
Not at all
5
4
3
2
1
0
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
Subject characteristics
25
26
35
34
Male
Female
Non-manual
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)
Manual
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
Effect of abstinence
Assoc with baseline
All values are greater than zero at p<.0001
vin
g
C
ra
To
t
Q
SU
F2
SU
Q
Q
SU
F1
To
t
S
PS
M
PS
S
St
Ti
M
PS
S
S
M
C
W
SW
S
W
Sh
iff
N
W
S
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
M
Eta squared
Sensitivity to abstinence: results
Consistency: analysis
• Select smokers who continued smoking
• Calculate correlation between 24 h score
and baseline score for each measure
All values are greater than zero at p<.0001
in
g
C
ra
v
To
t
Q
SU
F2
SU
Q
Q
SU
F1
To
t
S
PS
M
PS
S
St
Ti
M
PS
S
S
M
C
W
SW
S
W
Sh
iff
N
W
S
1
0.9
0.8
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
M
Pearson correlation
Consistency: results
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
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
t-value
Results
10
9
8
7
6
5
4
3
2
1
0
V vs P (A) B vs P (A) V vs B (A)
QSU F1
QSU F2
V vs P
(NA)
QSU tot
B vs P
(NA)
V vs B (N)
MNWS
t-values provide a comparable estimate of effect size; A=abstinent,
NA=non-abstinent
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
‘Better fewer, but better’
V. I. Lenin
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