The present study is the first to investigate the factor structure of the QSU-Brief reported by Cox et al. (2001)
. Additionally, it is the first psychometric investigation of the QSU-Brief to utilize the seven-point Likert-type scoring set from the original Tiffany and Drobes (1991)
study of the QSU. Using a sample of smokers presenting for treatment in clinical trials for smoking cessation, the QSU-Brief was evaluated using both exploratory and confirmatory factor analytic techniques. When the 10-item version of the QSU-Brief was initially examined using principal components analysis, the outcome revealed a two-factor structure that supported the results of Cox et al. (2001)
. However, when later tested using confirmatory factor analysis, the initial model found using principal components analysis showed an overall inadequate fit to the data. Due to the fact that items 2 and 5 displayed multiple dual loadings in the initial analyses of Cox et al. (2001)
, a model that excluded items 2 and 5 was tested, and this model also showed a poor fit. Only the third model, which included solely the most robust items from the original QSU-Brief analysis (Cox et al., 2001
), showed a good fit to the data. This model also demonstrated good reliability in the present study. In accordance with the results of Cox et al. (2001)
, the first factor represented an intention or desire to smoke, and the second factor related to relief of negative affect with an urgent desire to smoke. The items from Factor 1 of the 10-item QSU-Brief that relate to the rewarding aspects of smoking were not included in Model 3, so this aspect of craving was not captured by this model.
Thus, the current results seemed initially supportive of the factor structures reported by Cox et al. (2001)
. However, when subjected to confirmatory factor analysis, which allows for a more stringent analysis of the data, the evidence presented in the present study revealed that the data was best explained by a shortened form of the QSU-Brief. These results echo the findings of both Kozlowski et al. (1996)
and Toll et al. (2004)
, in which the initial factor solution of the 32-item QSU presented by Tiffany and Drobes (1991)
was not validated using confirmatory factor analysis. Instead, a model that included a shortened form of the QSU using only the most robust items from the initial factor analysis was found to fit the data best. Accordingly, in the present study, confirmatory factor analysis revealed that only the model using the most robust items from the initial factor analysis by Cox et al. (2001)
fit the data. It appears that it is only the most robust items of both the QSU and the QSU-Brief that are amenable to confirmatory factor analytic techniques.
Cox et al. (2001)
briefly discussed the possibility that the QSU-Brief might be used as a global craving measure. While this type of measure might be possible, the results of the Cox et al. study, the present study, and almost all of the studies analyzing the factor structure of the 32-item version of the QSU found evidence for a multidimensional nature of craving (Davies, Wilner, & Morgan, 2000
; Tiffany & Drobes, 1991
; Toll et al., 2004
). Indeed, even the study that argued for a unidimensional factor structure for the QSU (i.e., Kozlowski et al., 1996
) provided evidence for a two-factor structure for the scale. In the current study, the two factors appear to represent two distinct constructs as evidenced by the fact that the confidence interval test demonstrated good discrimination between the factors. This suggests that this shortened form of the QSU-Brief is made up of two distinct factors characterized by intention and desire to smoke in the first factor and relief of negative affect with an urgent desire to smoke in the second factor.
Regarding whether or not multiple aspects of craving should be assessed, there is growing evidence that such measurement provides a more thorough assessment of the nature of cravings, as differential outcomes across the two factors of the QSU have been demonstrated in several studies. For example, Eissenberg, Adams, Riggins, and Likness (1999)
examined the relationship between tobacco use and gender and found that women reported significantly lower scores than men in a gender by time interaction for Factor 2 of the QSU. Since gender is an important topic in nicotine and tobacco research (Piper, Fox, Welsch, Fiore, & Baker, 2001
), this is a potentially important finding, which would not have been possible without a multifactorial assessment of urges. In an investigation of the effects of alcohol consumption on craving to smoke, Burton and Tiffany (1997)
found that in comparison to placebo subjects, subjects drinking alcohol reported significantly greater urges to smoke on only Factor 2 of the QSU, with no effects found for Factor 1. As heavy drinking is prevalent among smokers (Shiffman & Balabanis, 1996
), this may be an important finding, which again relied on a multifactorial evaluation of tobacco craving. Clearly, an evaluation of both factors of the QSU made for a more thorough examination of cravings in the studies reviewed above, and important differences were found between the factors. These differences may be relevant clinically, as treatments may need to be tailored to address multiple aspects of craving. The QSU-Brief is a relatively new instrument, so there are no studies yet which show differential outcomes across factors like those described for the QSU. However, given the fact that several studies found differences across QSU factors, it is likely that such differences will be apparent for the QSU-Brief, and it will be important for future studies to determine if such differences are present.
There are limitations to making comparisons between the current study and the original QSU-Brief study (Cox et al., 2001
). First, the sample in the present study can probably best be compared to the outpatient clinic setting in Study 2 of Cox et al. (2001)
, given that these were smokers presenting for treatment, whereas their Study 1 used laboratory participants. Second, it may be inequitable to directly compare the results of the current study to those presented by Cox et al. (2001)
, due to the discrepancy in the scoring sets between the studies. Instead, it might be better to view them as two distinct questionnaires.
In conclusion, it is apparent from the present results that a shortened form of the QSU-Brief can be used with the original seven-point scoring set as a reliable assessment of the dual nature of urges originally proposed by Tiffany and Drobes (1991)
. Taken together with the results of Kozlowski et al. (1996)
and Toll et al. (2004)
, these findings provide evidence that only the most robust items from the QSU and QSU-Brief are amenable to confirmatory factor analysis. Furthermore, the shortened form of each of these two questionnaires using these robust items may provide a superior format of each scale both clinically and psychometrically. In light of the present findings, it will be important for future studies to confirm the two-factor structure of the five-item QSU-Brief presented in this study using both the seven-point and 100-point scoring sets, and it will also be essential for future studies to assess the predictive validity of the scale.