Results of our overall findings due to mood induction, excluding the individual difference factors of interest, demonstrated that negative mood increases smoking reward and smoking intake, consistent with some similar studies (Conklin & Perkins, 2005
) but not others (e.g., Weinberger & McKee, 2011
). As shown in , our results are also consistent with prior findings that smoking behavior during causes of negative mood other than tobacco abstinence fails to result in subsequent relief of NA (e.g., Perkins et al., 2010
; see also Baker et al., 2004
and Kassel et al., 2003
Regarding the factors of primary interest, we first discuss the findings due to subject sex and then those due to distress tolerance, since the latter also clearly involved sex differences. Importantly, NA and smoke intake responses to negative mood were generally greater in women compared with men, as hypothesized. Because exploratory analyses showed that the increase in NA due to negative mood was correlated with subsequent smoking reward and reward was correlated with subsequent smoke intake, the greater smoking response to negative mood in women versus men may stem from their greater NA response to negative mood. The sex differences in NA responses may be consistent with prior research indicating that compared with men, women report more severe NA in response to overnight tobacco abstinence (Xu et al., 2008
) and that they are less able to manage NA during cessation (McKee, O’Malley, Salovey, Krishnan-Sarin, & Mazure, 2005
). However, the fact that our mood induction procedure intentionally avoided effects due to tobacco abstinence indicates that this sex difference in the NA responses of smokers may extend to other causes of negative mood situations.
The smoking intake results may expand the breadth of sex differences in responses to negative versus neutral mood by suggesting that women increase smoke intake more than men under such conditions, which has often not been found in between-groups studies of mood (Fucito & Juliano, 2009
; Weinberger & McKee, 2011
). Our use of a within-subjects design may have enhanced the power to detect mood differences by sex, since each subject acted as his or her own control between mood conditions. On the other hand, future research should examine whether similar sex differences in smoking responses are observed with other specific causes of negative mood to determine the generalizability of our sex difference findings.
Our results for distress tolerance, by contrast, were very different than those above for sex differences alone. We found that NA during either mood induction condition was greater for those lower in distress tolerance as assessed by the self-report DTS (), similar to other research (Abrantes et al., 2008
). Yet, we found no differences due to DTS or the interaction of DTS by sex in the NA response to negative mood per se. So, contrary to our hypothesis, lower distress tolerance, whether assessed by the self-report or behavioral tasks, did not increase NA or smoking responses specifically to this nonabstinent cause of negative mood induction (compared with neutral mood), consistent with some prior research (Perkins et al., 2010
Notably, however, smoke intake responses to mood tended to run in opposing directions when we combined the factors of DTS and subject sex. The interaction of DTS by mood on smoke intake (puff volume and number) was significant for men and for women but in contrasting manner. While lower distress tolerance in men was related to greater smoke intake during negative mood and not neutral mood, generally the opposite interaction was observed in women. For women, lower distress tolerance was related to greater puff volume (marginally) and puff number (significantly) during neutral mood and not at all related during negative mood. One potential implication of these results is that distress tolerance and subject sex do not combine in additive fashion to increase smoking responses to negative mood.
An explanation for this pattern of sex differences in the way distress tolerance influences smoking responses to mood is not obvious, particularly since the increase in smoke intake due to negative mood was significantly greater in women compared with men, collapsing across DTS (bottom of ). Women lower in distress tolerance may be more likely to smoke maximally during either mood condition when given the opportunity (i.e., “ceiling effect”). If so, a further increase in smoking due to negative mood might be difficult within a prescribed period of time (e.g., the 14-min ad libitum smoking period of this study). By comparison, women higher in distress tolerance may generally smoke less during neutral mood, allowing greater opportunity to increase smoke intake during the negative mood condition (see bottom of ). Further research should examine different intensities of negative mood induction, as well as different types and durations of induction procedures, to determine whether the sex difference in effects of distress tolerance on smoking may depend on severity or type of negative mood induction and the duration of smoking access.
Regarding the different assessments of distress tolerance, we found no effects of distress tolerance as measured by the behavioral tasks of mirror-tracing and breath-holding duration compared with some smoking intake results for men and women assessed by the DTS self-report measure of distress tolerance. In addition, although breath-holding duration was correlated with mirror-tracing and self-reported DTS score, DTS and mirror tracing were not significantly correlated, confirming a clear difference between self-report and some task measures of distress tolerance (McHugh et al., 2011
One clear strength of this study was the greater statistical power due to use of a within-subjects design, to allow for stronger comparison of responses due to negative versus neutral mood induction. A similar strength was use of a fairly large sample, so that we could examine sex differences and distress tolerance, separately and combined, on responses to mood. Third, smokers smoked their own nicotine cigarette brand in unblinded fashion to better capture how these participants might respond to negative mood in the natural environment. Our use of both self-report and behavioral measures of distress tolerance may also be a strength (McHugh et al., 2011
), although distress tolerance may have had greater effects on smoking responses to mood if it had been assessed with other measures (e.g., Brown et al., 2009
Limitations of this research include the possibility that stronger effects of distress tolerance on smoking responses to negative mood may have been found in smokers with current mood dysregulation problems (e.g., major depression, panic disorder; see Fucito & Juliano, 2009
) or in smokers preparing to quit (Brown et al., 2009
). Also, as noted, our results could differ if smoking is assessed over a longer duration of exposure to negative mood or if negative mood varies in intensity or is caused by other types of situations. Results may differ as well for smokers who are older or generally higher in dependence than our sample or if subjects’ distress tolerance level is assessed after a period of tobacco abstinence rather than smoking as usual (Bernstein, Trafton, Ilgen, & Zvolensky, 2008
). Finally, although smoking here involved access to one’s own brand without blinding, to increase generalizability to smoking in the natural environment, findings could differ if smokers are blind to cigarette brand.
In conclusion, NA and smoking in response to experiencing negative versus neutral mood may be greater in women than men. Low distress tolerance was related to heightened NA under both mood conditions. Although distress tolerance may not have effects on the responses of all smokers to this negative mood induction, it may moderate smoking responses to mood conditions differently between women and men. Thus, the influences of subject sex and distress tolerance on smoking responses to negative mood may not be additive but rather interact in unexpected fashion.