Objective Social marketing is commonly proposed to counteract advertising and other messages that promote unhealthy products. However, public service campaigns can also ‘boomerang’ or ironically increase the unhealthy behaviours they are designed to discourage. The present study examined whether antismoking public service announcements (PSAs) could increase smoking behaviour immediately following exposure.

Methods In an experimental study, 56 smokers were randomly assigned to watch a short television segment with a commercial break that included either (1) a Philip Morris ‘QuitAssist’ PSA; (2) a Legacy ‘truth’ antismoking PSA; or (3) a control PSA. Smoking behaviour was assessed during a short break immediately following television viewing.

Results Participants who saw the Philip Morris antismoking PSA were significantly more likely to smoke during a break (42%) compared with participants in the control condition (11%), and participants in the ‘truth’ condition were marginally more likely to smoke (33%). These differences could not be explained by factors such as mood or level of addiction, and effects occurred outside of participants’ conscious awareness.

Conclusions These findings provide preliminary evidence that antismoking campaigns could ironically increase immediate smoking behaviours among smokers. The long-term benefits of proven public health campaigns, including ‘truth,’ are likely to outweigh any short-term boomerang effects. However, industry-sponsored messages in which companies have an economic incentive to increase consumption behaviours should be treated with scepticism and evaluated independently.