Background Gambling has been identified as an important public health issue. Independently developed public health gambling messaging is one potential component of a public health approach toward reducing gambling-related harm. The aim of this review was to systematically examine the evidence for the effectiveness of existing public health gambling messaging interventions, to inform future innovation and application.

Methods We searched four databases (MEDLINE, Embase, PsycINFO and ASSIA) from inception to May 2023. Studies of any design conducted in any country, reported in English, evaluating a public health gambling messaging intervention were included. We assessed study quality, extracted data, and completed a narrative synthesis.

Results Twenty-one papers met the inclusion criteria. The included studies were conducted in diverse settings, employed various study designs, and evaluated messaging interventions that differed in terms of their aims, and reported outcomes. The risk of bias was assessed as low to medium for 19 of the 21 papers. The interventions were categorised into three groups for discussion: general population-level messaging, safer gambling messages, and product risk warning labels. Few studies reported social cognitive outcomes (e.g., knowledge and awareness of risks and harms of gambling) or changes in intentions to gamble or engagement with gambling. The evidence - currently very limited - suggests that existing gambling messaging interventions are ineffective in changing behaviours but can raise awareness of gambling related harms. The review found evidence that the format and presentation of currently used safer gambling messages and product warning labels can be improved.

Discussion To our knowledge, this is the first systematic review to report on effectiveness of a broad range of gambling messaging interventions that are regarded as potentially important components of a public health approach to prevention of gambling related harms. There is a need to develop and test effective messages that can help prevent and reduce gambling related harm for the general population and for at-risk groups. Research is required for developing messages for people affected by gambling of others and for reducing gambling associated stigma in particular.