Comorbidity between depression and smoking moderates the effect of a smoking prevention program among boys in China.

Smoking prevention programs based on social influences have reduced smoking prevalence among youth. However, these effects have not been replicated consistently. It is possible that individuals and populations with different dispositional and behavioral characteristics will experience different program effects. This study explored a possible moderation of program effect by comorbidity between depression and smoking (CoM). Data for this analysis were from 2,450 seventh-grade youth (51% boys) who participated in the Wuhan (China) Smoking Prevention Trial (WSPT). WSPT was a randomized, controlled, 14-session, middle-school-based smoking prevention trial. Baseline and 1-year follow-up surveys were administered. The moderation effect between the program and CoM was tested on 1-year change in recent smoking. The CoM indicator was defined dichotomously as monthly cigarette use and high in depression level (among the top 20% in the sample). At baseline, a total of 26 girls and 60 boys were identified to have CoM. Among boys (but not girls), CoM significantly moderated the program effect on recent smoking (p = .01). The program effect among boys with CoM was 4.17 (95% CI 1.47-11.76) times larger than those without CoM. Among boys with CoM, the odds ratio of recent smoking was 0.18 (95% CI 0.06-0.55) for program vs. control condition. Among those without CoM, the program did not reduce the odds of recent smoking significantly (OR = 0.74, 95% CI 0.37-1.48). The study demonstrated that smoking prevention program effects can vary with individual characteristics, in this case comorbidity between depression and smoking. These findings may help explain the inconsistency in program effects across studies and populations. The findings also may contribute to the design of future programs to address the needs of defined populations and individuals with specific characteristics.