How can a ban on tobacco sales to minors be effective in changing smoking behaviour among youth? - A realist review.

The aim of the study was to understand, from the perspective of youth, how and under which circumstances a ban on tobacco sales to minors can be effective in influencing youth smoking behaviour. We searched Medline, Embase, and PsychINFO in February 2016. A systematic search for studies about a ban on sales to minors and smoking behaviour was performed. Only studies that addressed potential mechanisms were included, resulting in thirty-three studies. We extracted evidence from 26 quantitative, 5 qualitative, and 2 mixed-methods studies, explaining how the ban may be effective in reducing smoking behaviour, and contextual factors that may influence these mechanisms. We identified two mechanisms and three contra-mechanisms. First, when direct access to commercial sources is limited, cigarette consumption may be reduced because minors have restricted access to commercial cigarettes. Minors' access to social sources and the various ways in which they continue to buy cigarettes by circumventing the ban, are two contra-mechanisms that undermine this effect. Second, when the ban is strongly enforced, an anti-smoking norm may be created and adolescents may smoke less as a result. One contra-mechanism may possibly undermine this effect: the 'forbidden fruit' effect. Whether these (contra-)mechanisms occur depends on contextual and individual factors such as level of enforcement, the minors' social network, and their dependence on smoking. The ban can be effective if well enforced. However, minors' access to social sources and their ways to circumvent the ban should be addressed to achieve its full potential.