Smoking among U.S. adolescents has declined significantly in the past 20 years, but smoking still affects a significant proportion of this population and thus remains a major public health problem. A collaborative study examined the relationship between adolescent and adult smoking in seven international cohorts recruited in childhood and followed into adulthood.

Smoking information was obtained from 6,687 participants in childhood and adolescence (participants were six to 19 years old), and again during their 20s and 40s. Smoking cessation analyses were based on a sample of 2,465 participants who were smokers in their 20s.

The prevalence of daily smoking in their 20s was directly related to the intensity of childhood and adolescent smoking and inversely related to the age at which this smoking intensity occurred. For example, within the 18-to-19-year-old group, smoking prevalence for participants in their 20s ranged from 2.6% for those who never smoked during childhood and adolescence to 76.3% for daily smokers during that period. Patterns for prediction of smoking and smoking cessation in their 40s were similar. Smoking cessation in their 40s was generally inverse to the intensity of smoking during childhood and adolescence.

The authors advise that efforts should be made to prevent smoking exposure early in life, because it can lead to lifelong smoking patterns that are difficult to break.

Among the limitations of the study were that different questionnaires were used to assess smoking in different cohorts, and children may have difficulty responding to questions about smoking.