Background:
In recent years there has been a major decline in the smoking prevalence of under-16 year olds in Scotland, but relatively little decline smoking among 16-24 year olds. In addition, smoking uptake continues until the mid-20s, with smoking rates in 20-24 year olds higher than in 16-19 year olds. However, we know little about who is most at risk of becoming a smoker in this age group, what influences this, and how this relates to inequalities and smoking. This mixed-methods study aimed to address these questions.

Methods:
Detailed secondary analysis of the annual Scottish Health Surveys (SHeS) 2012-15 examined smoking behaviour in 16-24 year olds by key sociodemographic factors including gender, socio-economic status (area deprivation and educational/employment status) and other relevant health-related data including drinking behaviour and mental health status. After the quantitative analysis, qualitative purposive sampling of SHeS respondents was used to recruit a diverse sample (by smoking status, age, gender, economic activity) for in-depth qualitative interviews. Twenty-five interviews were conducted in 2016/17.

Results:
Smoking prevalence increased between 16-19 and 20-24 in both genders and all SES groups, and was significantly associated with SES, ranging in 16-24 year olds from 42% among those not in education, employment or training, to 24% among the employed and 13% among full-time students. Qualitative interviews highlighted the importance of educational and occupational transitions (to and from school/college and the workplace), social contexts and alcohol use in shaping smoking behaviour including uptake, consumption levels and quit attempts.

Conclusions:
Understanding the smoking beliefs, behaviour, social and occupational contexts and transitions of 16-24 year olds is vital for developing effective policies to reduce smoking and inequalities in smoking in this key age group. This research demonstrates the nature of inequalities in smoking in Scottish young adults, which has implications for smoking prevention and cessation strategies.