“Teenagers who watch films showing actors smoking are more likely to take it up, new UK research suggests,” reported BBC News. It said a study of 5,000 15-year-olds looked at their exposure to smoking on screen, and whether or not they had tried smoking.
This study found that 15-year-olds who were most exposed to seeing smoking in films were more likely to have tried a cigarette than those least exposed, and were also more likely to be current smokers.
This is a large, well-conducted study in more than 5,000 teenagers and its findings will contribute to the debate on the factors that encourage adolescents to take up the habit. The study has several limitations, however, and while it provides a valuable snapshot of teen film viewing and smoking habits, it cannot prove that watching smoking on screen contributes to teenagers starting smoking.
Reducing smoking in young people is an important issue and it is probable that role models in films play a part. However, it is unclear at this stage whether reclassifying films featuring smoking to certificate 18 will have this effect. Further research is needed.
Where did the story come from?
The study was carried out by researchers from the University of Bristol and Dartmouth Medical School, USA. It was published in the peer-reviewed medical journal Thorax . Funding was provided by the US National Institutes of Health and the American Legacy Foundation.
The newspaper reports were fair, although they did not cover the study’s limitations. Both the BBC and The Independent used figures from the study that had not been adjusted for all the factors that might have been an influence on teen smoking habits. They both reported that teenagers who were most exposed to films in which characters smoked were 73% more likely to have tried a cigarette. However, when this figure was adjusted for confounders, these teenagers were found to be 32% more likely to have tried a cigarette.
What kind of research was this?
This was a cross-sectional study designed to assess whether there is any association between depictions of smoking in films and adolescent tobacco use. The authors say there is increasing evidence that exposure to risky behaviour in the media (for example via TV programmes and films) is associated with risky behaviour such as tobacco and alcohol use in childhood and adolescence. They say that while film ratings systems address issues such as violence they do not address the issue of smoking.
The researchers say that previous research from other countries has shown that smoking attitudes and the behaviour of adolescents is influenced by smoking seen in films, but it is unclear whether this association applies to adolescents in the UK.
In this study, the researchers wanted to investigate whether there was an association between watching smoking on screen and smoking behaviour in a large population of 15-year-old adolescents in the UK.
What did the research involve?
Data for this research were obtained from a large ongoing Bristol-based study that is looking at the health and development of children. The Avon Longitudinal Study of Parents and Children (ALSPAC) enrolled 14,500 pregnant women with an expected delivery date from 1991 to 1992. Detailed information has been collected using questionnaires completed by mothers and by their children after they reached the age of seven years.
The researchers looked at data on both smoking and film collected from more than 5,166 15-year-olds in the study. A computer-assisted interview was used to ask adolescents whether they had seen 50 randomly selected films, drawn from a list of 366 popular contemporary films comprising the top 70 US box office hits released between 2001 and 2005. The number of smoking occurrences in each film was counted by trained assistants. The number of occurrences in each film was identified as the total exposure and these were classified into four categories ranging from highest to lowest.
The teenagers were also asked questions about smoking, in particular whether they had ever tried a cigarette and whether they smoked currently.
The researchers also took into account possible confounders, information on which had been collected over time. These included breastfeeding, childhood disorders, social class, parental and childhood behaviour, current alcohol use, other social and environmental factors and whether their friends smoked.
The researchers created six different models that took into account different combinations of these confounders, and looked at the association between exposure to films containing smoking and smoking habits in each of these models. They did this to see whether adding or removing the influence of things like family smoking, peer pressure and social class affected the strength of the association.
They also looked at data from all existing cross-sectional studies on the effects of smoking in films and summarised these in a meta-analysis. They used a systematic search strategy to identify such studies.
What were the basic results?
The higher the exposure to smoking in films, the higher the risk of teenagers having tried a cigarette.
- Those in the highest category of exposure to smoking in films were 73% more likely to have ever tried smoking than those in the lowest category of exposure (RR 1.73, 95% CI 1.55 to 1.93).
- After adjusting for all the confounding factors, including alcohol use and peer group smoking, in the sixth model, this relative risk dropped to 1.32.
- Those in the highest category were 47% more likely to report they currently smoked after adjusting for age, gender, social factors and family influences. The researchers thought this was the most representative model (RR 1.47 95% CI 1.07 to 2.01).
- In the analysis of current smokers in which other factors including behavioural factors like problems with attention, depression or anxiety were adjusted for, the relative risk dropped further (RR 1.34, 95% CI 0.95 to 1.87) and became non-significant.
The researchers’ meta-analysis of existing studies found that viewing smoking in films doubled the likelihood of having tried a cigarette (combined RR 2.13 95% CI 1.76 to 2.57) and increased the likelihood of currently smoking by 68% (combined RR 1.68, 95% CI 0.40 to 2.01). The meta-analysis included six previous studies and three that were published in the current issue of Thorax , including the one from Bristol.
How did the researchers interpret the results?
The researchers conclude that their study provides evidence that adolescents in the UK and elsewhere who are exposed to smoking in films are more likely to start or try smoking. They say this finding justifies a review of film ratings so that they take into account scenes with people smoking.
One of the strengths of this study is that the researchers carried out several adjusted models to check for the influence of confounding factors. They also present the results of a meta-analysis that puts their study in context and includes the findings of other studies.
The study also had some limitations:
- As a cross-sectional study, the study cannot establish cause and effect, so it cannot say that viewing films where characters smoked caused teenagers to start smoking. It is possible that teenagers in the study tried a cigarette or started to smoke before they had seen films containing scenes of smoking.
- The researchers relied on teenagers self-reporting both what films they had seen and whether they smoked or had tried smoking, which could affect the reliability of the study’s results. As the researchers also point out, they only recorded whether films on the list had been seen, not the number of times the films had been seen.
- Although the researchers tried to adjust for confounders, it is possible that other factors, both measured and unmeasured, influenced teen smoking habits.
In conclusion, this large study is a valuable contribution to the discussion about teen smoking habits. However, due to the design of the study and the previously mentioned limitations, the study cannot prove that exposure to smoking on screen makes adolescents more likely to smoke. While reducing the number of teens taking up smoking is an important issue, it is still unclear whether classifying such films as certificate 18 would have this effect. Further research and debate is needed.
Analysis by Bazian
Edited by NHS Website
Links to the headlines
The Independent, 20 September 2011
BBC News, 20 September 2011
Links to the science
Thorax [Published online first] August 25 2011