Our results confirm an association between exposure to smoking in films and youth smoking in the UK. This association is consistent with the association reported in other populations. At age 15, adolescents in this Bristol-based birth cohort with high exposure to smoking in films were almost twice as likely to initiate smoking as those with low exposure. However, the influence of smoking depictions in films was attenuated when family factors including parental monitoring were included in the model and attenuated further when behavioural factors were included. A similar pattern is seen for current smoking status, but that effect is largely attenuated by the inclusion of family influences. The meta-analysis shows that results from cross-sectional studies conducted in the USA, Mexico, Germany and the UK give consistent results for the association with smoking onset and current or established smoking, despite different study characteristics.
One strength of this paper is that this birth cohort afforded a rich array of individual and family descriptors collected prospectively over time and not previously controlled for. Even after controlling for social, family and behavioural factors and mediating variables, increased exposure to smoking depictions in films increases the risk of smoking initiation in adolescence. This study is also consistent with findings from other studies in which alcohol use and having peers who smoke12,23,24,33
attenuate the effect of exposure to smoking in films on smoking initiation. Further research is required to examine mediating and moderating effects of these variables and to investigate the mechanisms by which smoking depictions inform and shape the attitudes and behaviours of adolescents.
The paper is subject to several limitations. We gave the study participants a list of films but only recorded those they had seen; we have no record of the number of times films were seen or of films not seen. Also, the data for peer behaviour and alcohol use—mediators which reduce the association between exposure to smoking depictions and smoking initiation—were collected concurrently so we cannot determine whether these relationships are causal or the likely direction of causality. Finally, as with most large cohort studies, attrition of those in more adverse circumstances could affect our ability to generalise results to groups who were more likely to drop out of the study. However, previous work using ALSPAC data13
has shown that drop-out from the ALSPAC cohort is selective and therefore regression models are likely to be only marginally affected.
Given the likelihood that the observed association may be causal (as noted by the US National Cancer Institute),34
it is important to consider public health implications as exposure to smoking depictions is universal in this instance, with virtually all adolescents reporting that they had seen at least one film from the list. In the subsample of the cohort who had seen 69 or more smoking depictions in films, the proportional attributable risk for the association between smoking depictions and smoking onset is large, in the order of 30%. It should further be noted that young people in the UK are exposed to 28% more smoking depictions in cinema films than youth in the USA because 79% of films rated as `adults only' in the USA are rated as suitable for young people in the UK.35
Finally, randomised controlled trials to investigate the influence of smoking depiction on smoking behaviour would almost certainly be deemed unethical, so observational studies may be the most rigorous that we can achieve.
If the dose-response relationship between smoking depictions and smoking initiation is causal—as shown in other cross-sectional and longitudinal work36
—then, in the first instance, preventing adolescents from being exposed to smoking depictions by raising the certification to `18' in the UK is likely to lower smoking rates among youth. Given that smoking depictions in films are not consistent with the ban on smoking in public places in the UK and that the relationship may be causal, a precautionary principle should be pursued. Films ought to be rated by exposure to smoking in the same way that they are currently rated by level of violence: smoking and its adverse consequences are certainly a larger public health problem. Such a policy would also make the movie ratings system consistent with the ban on tobacco advertising in all other media.
The results of this study are consistent with others that have examined the association between exposure to smoking depictions in films and smoking initiation. In this population cohort, young people exposed to the greatest number of smoking depictions are 73% more likely to have tried smoking and almost 50% more likely to be current smokers than those exposed to very few smoking depictions. This association remains even after adjustment for confounding and mediating variables. Given the adverse effects of tobacco use on health, the findings of this study surely justify a review of the film rating categories in the UK and serious consideration given to incorporating smoking into the ratings system.