Letters

Stages of change model for smoking prevention and cessation in schools

Authors applied adult dose for smoking to adolescents when smoking behaviour is different in the two

Authors' reply

Authors applied adult dose for smoking to adolescents when smoking behaviour is different in the two

EDITORMy colleagues and I have read the article by Aveyard et al on smoking prevention and cessation in schools, which examines the use of computer delivered expert system interventions that we have developed.¹

For unreported reasons, Aveyard et al applied our adult dose for smoking to an adolescent population. In our standard adult protocol we provide three expert system interventions over six to 12 months. Aveyard et al provided three expert system interventions to adolescents over a comparable period of time. Our behaviour change protocol for adolescent populations calls for six to eight expert system interventions over two academic years. One of the reasons our treatment with adolescents is at least twice as long, with more expert system interventions, is that smoking increases over a two year period with adolescents, whereas it decreases with adults. Why would Aveyard et al expect an adult dose for smoking to be effective with adolescents? I know of no evidence, and Aveyard et al provide no evidence or rationale, for applying our adult dose of expert systems to adolescents.

We will soon be reporting on the important pattern of results that were produced when our two year adolescent protocol was applied to an adolescent population.

James O Prochaska, director. 
Cancer Prevention Research Center, University of Rhode Island, Kingston, RI 02881, USA jop{at}uri.edu

Competing interests: I am one of the developers of the expert system under discussion. The expert systems for smoking are owned by the University of Rhode Island and are licensed to Johnson and Johnson Health Services. A sublicence has been developed with Nelson Communications in the United States and Public Management Associates for commercial use in the United Kingdom. Pro-Change Behavior Systems, LLC, of which I am a principal, provides research and development services to these two companies.

Authors' reply

EDITORProchaska implies that there is a well known adult dose and an adolescent dose of the expert system. The only evidence on how many doses of the expert system should be used is from a trial in adults, and that evidence suggests that one is enough.¹ Prochaska and colleagues' only other published study on the transtheoretical model expert system in adolescents used three sessions.² There is no evidence on which to base a decision about how many sessions adolescents might need.

Prochaska advances the argument that because the prevalence of smoking in the group of adolescents is changing rapidly the individuals in that group are less susceptible to change by the intervention and need more sessions to achieve the effect that adults would achieve with fewer sessions. This does not follow. Our data show that 37% of adolescents who smoked regularly were preparing to stop smoking, compared with the 20% that is typical in adult populations.³ Such individuals are more likely to have quit at one year than individuals in earlier stages of change.⁴ This reflects itself in the high quit rates achieved by both intervention and control groups (more than 25% at one year). On this basis, it seems more likely that the expert system for adolescents, the only one that can be compared with the system for adults, should be more successful and require fewer sessions, yet we found no effect.

A better explanation for the failure of the intervention is one advanced by Reid.⁵ Teenage smokers have a variety of smoking histories and do not construe their behaviour in the same way that questionnaires do. Perhaps the concept of being a regular smoker is foreign to most young teenage smokers, as is the idea of needing to go through a process to stop smoking, so the expert system's messages were lost on them.

Paul Aveyard, lecturer in public health medicine. 
p.n.aveyard{at}bham.ac.uk

K K Cheng, professor of epidemiology. 
Terry Lawrence, senior health development adviser. 
Department of Public Health and Epidemiology, University of Birmingham, Birmingham B15 2TT