These findings confirm the predictive role of several key clinical, psychological, and cognitive factors in predicting abstinence for this highly dependent lower SES group of smokers. These findings suggest that this population typically manages high levels of negative affect, dependence, and stress levels, and in this context smoking to reduce negative affect plays a significant role in reducing the likelihood of achieving abstinence. This is one of the few studies that demonstrate that an externally focused locus of control, steeper delay discounting, and greater cognitive impulsiveness independently predict a lesser likelihood of abstinence and suggests that these factors play a role in treatment outcomes for lower SES groups.
Externally focused individuals appear to experience greater levels of stress and be less likely to achieve abstinence from smoking after treatment. The positive correlation between locus of control and stress level is unsurprising given that the two constructs are both conceptually related to perceived control over external events. Greater stress levels are consistently associated with less perceived control over external events.97
Several items on the PSS assess perceived control (ie, “How often have you felt that you were unable to control the important things in your life?”).59
Because externally focused individuals attribute reinforcement as under the control of external agents such as luck, chance, fate, or powerful others, they are likely to perceive less control over important events in their lives and thus are likely to experience greater levels of stress. Although not a finding here, greater stress levels have also been associated with higher dependence levels and poorer treatment outcomes.60, 98
These findings suggest that research is needed to further explicate the relationship between locus of control, stress, and perceived control in order to better understand how to assess and address these important prognostic factors. This might be particularly important for lower SES smokers as they appear to endorse a more externally focused locus of control which may be reinforced by cultural factors.11
Additionally, the cognitive and physiological ramifications of externally focused individuals chronically experiencing higher levels of stress have the potential to be far-reaching.
Baseline measures of delay discounting were strong predictors of abstinence after treatment. Three different delay discounting measures predicted abstinence including hypothetical discounting of $100 and $1,000 and the mean discounting rate of hypothetical $100, $1,000, and real $100. (Note: The estimated effect of the discounting rate for real $100 [OR = .887, one-sided p
= .069] was nearly as strong as the others, but the reduced variance of real $100 discounting rates [relative to the other three] might have prevented it from reaching statistical significance.) These results support previous findings that indicate increased discounting predicts less success with abstinence.37–39
Given the strong relationships between delay discounting and smoking status in cross-sectional studies, previous studies have questioned whether individuals who, at baseline, discount more steeply (ie, have strong preferences for smaller, sooner rewards) are simply less successful at achieving abstinence, or if individuals who stop using tobacco begin to discount less steeply over time. If the latter statement were true, we would be unable to predict abstinence from the natural variability in discounting rates. Lower discounting rates would emerge from the process of quitting or being quit. If the former statement were true, the natural variability in baseline discounting rates would predict treatment success, as was the case in this study.
These findings suggest that delay discounting is clinically relevant in predicting abstinence outcomes from CBT for tobacco dependence. Delay discounting might be a productive target for new assessment and therapeutic approaches. These findings also suggest that various measures of discounting future rewards (ie, hypothetical and real, $100 and $1,000) are similarly effective in predicting treatment outcomes. The propensity to more steeply discount delayed rewards has the potential to become a behavioral marker alerting clinicians that these individuals might have more difficulty quitting and might need additional or special attention. Discounting rates could be evaluated during the initial assessment along with dependence and stress levels as well as the propensity to smoke in response to negative affect, and other factors. More research is needed to determine the levels of discounting that place a smoker at higher risk for relapse after treatment. More research is also needed to discover the manner in which clinicians might tailor treatment for individuals who discount more steeply. Similar to highly dependent smokers, more intensive and longer treatment, including combination drug therapies might be required for better treatment outcomes for steep discounters. Alternatively, similar to highly stressed smokers or smokers prone to dysphoria, CBT that targets cognitive errors and/or reframes cognitions involved with impulsiveness, the propensity to prefer smaller, sooner rewards, and the perceived contingencies on rewards might be required for better treatment outcomes for steep discounters.
Increased impulsiveness and the propensity to delay reward are also associated with decreased activity in the prefrontal cortex relative to the limbic areas, while the preference for immediate rewards is associated with a relative increase in activity in the limbic system relative to the prefrontal cortex.13
Because there are distinct areas of brain activity associated with immediate versus delayed rewards in delay discounting tasks and delay discounting tasks predict abstinence, these findings also suggest that abstinence might be associated with these distinct areas of brain activity as well. If so, then increasing or decreasing activity in these specific areas might also lead to new assessment and therapeutic approaches. Increasing activity in the prefrontal cortex using direct stimulation or repetitive transcranial magnetic stimulation has been shown to temporarily reduce risky or impulsive decision making,99
and in one case actually reduced the number of cigarettes smoked in the hours after stimulation.100
Similar to the way that our current repertoire of approved cessation medications assist with cessation by attenuating the experience of withdrawal, these findings suggest that we might be able to augment treatment by attenuating the propensity to make impulsive decisions by increasing activity in the prefrontal cortex.
This study has a number of strengths and limitations. Among the strengths are that this study provided a highly intensive behavioral treatment with a full range of evidence based components in the absence of medications. This allowed us to evaluate the response to cognitive-behavioral therapy alone without confounding the treatment response with response to medications, which might have produced physiological changes that would have confounded our results. Furthermore, if steep discounters are similar to highly dependent individuals and simply respond better to more intensive, combination treatment, the addition of medications might have attenuated the predictive utility of the delay discounting tasks. A further strength of this approach was its ecological validity, as minority and lower income smokers are less likely to use nicotine replacement or other medications for cessation.5, 101–106
Moreover, a minority of publicly funded treatment programs consistently offer free or low-cost medications; only about one-third of quitlines in the United States provide free or low-cost medications and then only to eligible participants.107
Nonetheless, our participants were characterized by factors strongly associated with more difficulty achieving abstinence (ie, high dependence, negative affect, and stress levels and lower SES) and only a small number of participants achieved long-term abstinence. In all likelihood, more participants would have achieved abstinence if medications were included. A larger group of abstinent smokers would have increased our ability to detect statistical significance and would have allowed us more freedom in our choice of analyses.
Additional limitations include the number of participants who were lost to follow-up. While very little dropout occurred during treatment, a smaller group of participants regularly attended the follow-up assessments .As with many lower SES groups, many participants were highly mobile, depended upon pay-as-you-go forms of communication, and were difficult to track. Given that 51% of participants were unemployed at baseline, it is unsurprising that some participants needed to relocate over the course of 6 months to find work. Use of GEE analyses helped to minimize the effects of missing data on the outcomes, but missing outcome data were nonetheless a limitation that must be considered when interpreting these findings. Another consideration is that the study did not examine the effects of SES level. As such, the findings cannot directly address the extent to which these factors are associated with treatment outcomes for individuals of middle and higher SES; however, given the importance of identifying successful treatment strategies for lower SES individuals, this study verifies that these prognostic factors, both established and novel, are indeed important determinants and are potentially important targets for tailoring interventions for this population. Finally, although the use of CBT without pharmacotherapy in this study is a strength in some ways, it is also a limitation. The current findings may generalize to lower SES smokers receiving pharmacotherapy, but the current data cannot speak to that question directly.
Future research needs to elucidate relationships among delay discounting, impulsiveness, stress, locus of control, SES, and ability to achieve abstinence for tobacco users with and without the use of CBT and medications. These interrelationships are particularly important in light of the fact that some of the largest effect sizes observed in this study were for stress and discounting, and there is evidence that powerful state factors make discounting more impulsive. This may also be the case for stress. Certainly this sample was characterized by high levels of dependence and were thus subject to high levels of nicotine withdrawal which have both been shown to make discounting more impulsive.31, 36, 108
Moreover, these smokers also reported high levels of stress which has been shown to interact with impulsiveness to increase the vulnerability for another addictive substance, alcohol.24
Thus, for lower SES smokers, high levels of nicotine dependence, impulsiveness, and the financial stresses of daily life may interact to create adverse intrapersonal conditions for smoking cessation. Paradoxically, there are clear environmental factors to motivate lower SES smokers to quit, such as the associated cost, that need to also be taken into account. Finally, future studies will be necessary to develop and test assessment methods and cut-off scores for use by clinicians for delay discounting, locus of control, and impulsiveness measures as well as the efficacy of new strategies to address impulsiveness, the propensity to discount the value of future rewards, and to reframe an externally focused locus of control. These strategies include both cognitive-behavioral strategies and novel approaches such as neurocognitive training.109
Progress in these domains will be essential for clarifying the present findings and translating them into improved smoking cessation outcomes for lower SES smokers.