Health warnings in the form of pictures or text on the back of cigarette packets are common in many countries, serving to deter smokers from the habit. But according to a new study, they have little impact on teen smokers.

In the US, cigarette packets carry health warnings in the form of text only. In 2011, the US Food and Drug Administration (FDA) published a final rule stating that health warnings in the form of images must be present on all cigarette packets to deter smokers.

However, this ruling was challenged in court by tobacco companies, and the rule was dropped.

But in many countries, such as the UK, this ruling is very much in place, with some pictures covering more than 75% of the main surface area on a cigarette packet, alongside text warnings. Researchers from the UK wanted to find out exactly what effect this had on smokers, particularly teenagers.

They conducted a study involving two waves of a Youth Tobacco Policy survey of adolescents 11 to 16 years of age. One survey was completed in 2008 by 1,401 teens, and the other in 2011 by 1,373 teens.

For each survey, the same text warnings appeared on the front and back of the cigarette packets, while pictorial health warnings were present on packets for the 2011 survey.

All teenagers were required to share their thoughts regarding the visibility and impact of the warnings, and their responses were scored on a sliding scale of 1 to 5. They were asked: