The HS intervention, with its proactive identification and recruitment of teen smokers and personalized MI plus CBST telephone counseling protocol, showed evidence of effectiveness for both long- and short-duration smoking abstinence endpoints and for progress toward smoking cessation. This is the first adolescent smoking cessation trial to report statistically significant increases in 6-month prolonged abstinence, as measured 12-months-postintervention-eligibilty, among a large population of adolescent smokers in a nonmedical setting. In addition, treatment effects for the shorter-term duration outcomes of 30- and 7-day abstinence among daily smokers (8.5%, P
= .006 and 10.5%, P
= .002, respectively) were about three times the treatment effect of 2.9% reported by Sussman et al. (10
) in their meta-analysis.
Contributing to the validity of these results are elements of the trial's design and conduct: 1) 50 high schools that were representative of the State of Washington; 2) a large number of smokers (N = 2151); 3) identification of study participants before randomization, ensuring that participant selection was the same in both the control and experimental groups; 4) random assignment of intervention condition by group (high school); 5) explicit consideration of intraclass correlation of endpoint within schools, both in determining sample size necessary to achieve needed statistical power and in analysis method; 6) low (11%) attrition; 7) a prolonged-abstinence (over the 6-month period before the outcome survey completion) outcome measure; 8) conservative determination of cessation, requiring consistent reports of abstinence across multiple outcome measures; 9) implementation of telephone counseling in accordance with an explicit protocol and with documented acceptable fidelity of MI as assessed using the Motivational Interviewing Treatment Integrity Code (84
); 10) a statistical analysis (permutation inference) based on the randomized assignment of experimental condition, free of modeling or distributional assumptions; and 11) control via stratification of the baseline difference in daily smoking prevalence between experimental and control schools.
The positive results for effectiveness of the HS intervention are important for several reasons. First, the results show that intervention can help teens quit smoking, the number one cause of preventable death in the United States. Second, the results were achieved among older adolescent smokers. Thus, intervention effectiveness was demonstrated during a developmental period when adolescents are at high risk for smoking initiation, escalation, and relapse (3
) and for members of an age group (ages 18–24 years) whose smoking prevalence exceeds 23%, the highest of any age group in the United States for 9 consecutive years (86
). Third, the telephone counseling component of the intervention used a promising therapeutic model––MI plus CBST—and thus contributes important empirical results to the field of youth smoking cessation. Fourth, the intervention effect was demonstrated in the HS trial among a proactively identified population in which more than 93% of eligible high school juniors completed a baseline survey, and nearly 90% of identified smokers in experimental schools became eligible for the intervention. Thus, this population included smokers who typically would not initiate contact with quitlines or other cessation programs and both daily and less-than-daily smokers. Moreover, because this trial cohort well represented all smokers in 50 high schools, the trial results are generalizable. Finally, 72% (691 out of 948) proactively identified, eligible smokers participated in the intervention and more than half (499 out of 948) completed all of their scheduled counseling calls (54
), demonstrating that substantial reach can be attained and that adolescents can be successfully recruited and retained in smoking cessation interventions.
These results support the use of MI in smoking cessation intervention for teens. They are contrary to Hettema's 2005 review (89
), which reported a lack of empirical support for the efficacy of MI for smoking cessation, but are consistent with subsequent literature in which one study of “pure” MI (90
) and three studies testing MI in combination with other therapeutic modalities (23
) reported statistically significant improvements in adolescent smoking cessation.
Although this two-arm trial cannot determine which components of the intervention were responsible for the positive results, five main features of the HS intervention are worth highlighting as possibly critical to the results obtained: 1) The use of MI—a motivation-enhancing modality that is client centered, nonjudgmental, and respectful of teens’ autonomy, views, and choices—in combination with CBST. 2) Personalization of the intervention so that both the counselor and client focus on the specific needs and issues most relevant to each adolescent smoker. 3) The proactive nature of each phase of intervention: identification of smokers in the larger population, personal outreach to all smokers and selected nonsmokers, and counselor-initiated delivery of the telephone counseling. 4) The trial's inclusion of daily smokers and less-than-daily smokers, as well as nonsmokers, in the intervention, serving to help remove any stigma teens associate with participation in smoking cessation programs. This feature together with personal outreach and counselor-initiated delivery of the telephone counseling seems helpful in recruiting teen smokers who typically would not self-select for intervention. 5) High-quality intervention implementation, including motivated and skilled counselors, use of a detailed protocol, thorough counselor training, and attentive supervision.
Two other randomized controlled trials of teen smoking cessation found statistically significant intervention effects on 30-day or longer smoking abstinence at least 6 months postintervention: Hollis et al. (23
) and Pbert et al. (30
). These trials had intervention features similar to the HS trial in that they proactively identified and recruited participants within targeted populations: Hollis et al. (23
) and Pbert et al. (30
) targeted all teens with scheduled appointments at participating pediatric or family practice clinics for recruitment; the HS trial targeted all smokers enrolled as 11th graders in 50 public high schools. All three trials involved both nonsmokers and smokers in their study populations and defined smokers as having smoked in the past 30 days, thus including both daily and nondaily smokers. All three trials tested multicomponent interventions that were personalized to the smoker and that used MI. Hollis et al. (23
) tested a transtheoretical model–based intervention that included brief physician advice, an interactive computer program, and individual counseling by health counselors using MI; advice was “highly individualized” to the participant's smoking status and readiness to change. Pbert et al. (30
) tested the 5A model (Ask, Advise, Assess, Assist, and Arrange) (9
) combined with MI and behavior change counseling that was delivered by physicians and older peer counselors and tailored to the smoker's current smoking status and responses to key questions. The HS intervention was delivered by telephone counselors, used MI plus skills training, and was personalized to the participant's current smoking status, readiness to change, and stated interests and concerns.
Considering the scarcity of high-quality trials that had positive findings, results from these three trials are important in informing future development of effective teen smoking cessation intervention. Results from the three studies strongly support interventions that are proactive in identifying and recruiting smokers, include nonsmokers as well as smokers, are personalized to the individual smoker, and incorporate motivation enhancement. The effect sizes reported from these three studies were greater than the overall treatment effect size of 2.9% (difference in percent quitting) estimated in a recent meta-analysis of 48 controlled studies of teen smoking cessation, many of which included only those smokers who self-selected for cessation treatment (10
). The effect sizes reported in these three studies suggest that with motivation enhancement, smoking cessation intervention can be as effective among unmotivated as among motivated smokers. More important, because proactive approaches are able to reach more smokers, interventions that proactively identify and recruit smokers and address issues of motivation may have a broader public health intervention impact.
It should be emphasized that proactive identification of smokers entails the responsibility to guard confidential information about smoking status against any intervention procedure that could violate confidentiality assurances. For teen smokers, this is especially important because revelation of their smoking status could result in parental discipline or school punishment, which in turn could discourage their participation. In this trial, confidentiality was protected by including selected nonsmokers in the intervention and not revealing smoking status (whether smoker or nonsmoker) when contacting the parent and teen for recruitment.
There are some limitations to consider in evaluating the results of our study. First, because the intervention used more than one component (ie, telephone counseling plus the adjunct Web site and school-based components), integrated use of two therapeutic modalities (MI and CBST), and incorporated multiple strategies to increase reach (eg, personalization of the intervention, telephone delivery), the results from this two-arm trial cannot determine the individual contributions to intervention impact from any specific component or feature. In particular, it is not possible to isolate the effects of the MI from the CBST in this multicomponent intervention. Also, the role of dose (number of calls) in intervention effectiveness cannot be determined, because the number of calls was personalized to the participant's readiness to quit, interest, and response to the intervention.
Second, in spite of the proactive recruitment of teen smokers, nearly 35% of smokers (367 out of 1058) did not complete even one telephone counseling call. Three factors contributed to this result: lack of parental consent for participation of some minor-aged smokers (110 parents either did not reply or declined), failure to reach some eligible smokers despite numerous contact attempts (n = 131), and declines by teen smokers (n = 126). Future trials should consider additional or new methods for overcoming these causes of nonparticipation.
Third, despite efforts to increase enrollment by racial and ethnic minorities, the trial's enrollment of these groups, although reflective of the community populations in the 50 participating schools, was too small (25%) to allow for minority-specific investigations. Nonetheless, the study's emphasis on proactive population-based outreach and recruitment, proactive intervention delivery, and real-time personalization of the intervention to the individual smoker suggest the possibility that this intervention might also work well in racial and ethnic minority populations. Certainly, this is an area for future investigation.
Fourth, the methods used in this trial for proactively identifying smokers may need to be modified and streamlined for dissemination. Although the proactive identification of adolescent smokers via classroom survey with mail and telephone follow-up was successful in our study, and could be replicated in other organizations with access to teens, it may in a dissemination model need to be less intensive with respect to contacting absentees (at a cost of identifying fewer smokers). Regarding parental consent, whereas our method of obtaining consent (using mail and telephone to contact parents before contacting teens) is more effective in reaching parents and obtaining consents than other common methods (eg, contacting eligible students and asking them to obtain written consent from their parents), it is also more costly due to the personnel labor involved. To reduce such costs, two alternatives could be considered: proactively recruiting teen smokers after they reach the age of 18 years, or obtaining an Institutional Review Board waiver of parental consent, appropriate when delivering a minimal risk intervention to older adolescents (40,42,45,92–96).
The current trial's promising findings suggest multiple areas for future research. First, it will be important to replicate these encouraging findings both in general populations of adolescents and in other underserved and high-risk populations. It would also be useful to test a strengthened intervention designed to help additional youth not reached by the current intervention and, possibly, to conduct a multiarm trial to isolate the effects of the MI and CBST intervention components. Also, future trials are needed to further explore treatment-by-gender interactions. Second, additional analyses of mediation and intervention process data may lead to better understanding of how the intervention helped smokers to quit and how it, and counselor training, might be improved to increase intervention effectiveness. Third, continued follow-up of the trial cohort is important to determine to what extent the treatment effects observed at 1 year postintervention reported here persist into adulthood. A finding that effectiveness of an intervention delivered in late adolescence could endure into young adulthood, a developmental period of increased smoking initiation, escalation, and relapse (3
), would have important public health implications for reducing smoking prevalence. Fourth, close evaluation of the characteristics of smokers not helped by current intervention strategies will likely be important for further development of interventions with broader effectiveness. Fifth, further research on the understudied population of less-than-daily smokers is warranted to learn more about how to motivate and assist them to quit: They comprise more than 60% of all teen smokers and are at risk for smoking escalation during young adulthood (3
). Indeed, increasing cessation among less-than-daily smokers is an important research goal that, if successful, would contribute to reducing young adult smoking prevalence rates. Finally, further methodological improvement is needed in the rigor of randomized trials of teen smoking cessation (eg, 22,14,11).
In conclusion, the results of the HS trial show that proactive identification and recruitment of adolescents via public high schools can produce a high level of intervention reach, and that delivery of a personalized MI plus CBST counseling intervention via the telephone by well-trained counselors is effective in increasing teen smoking cessation. Both daily and less-than-daily teen smokers participate in and benefit from telephone-based smoking cessation intervention.