Competing interests: We have read and understood BMJ policy on declaration of interests and declare the following: ST has received funding for gambling research from the Australian Research Council, the Victorian Responsible Gambling Foundation, Healthway, the NSW Office for Gaming, and Deakin University. She is a board member for the International Confederation of Alcohol and Other Drug Research Associations and is a member of the Gambling Harm Prevention Advisory Committee of LotteryWest, a statutory body established by the West Australian government. She is not paid for these roles. She is editor in chief of Health Promotion International. MM has received funding from NIHR for a doctoral fellowship to research public health aspects of gambling and is president of the BMA (but is writing in a personal capacity). MD has received funding for gambling research from the Australian Research Council, Healthway, and the Victorian Responsible Gambling Foundation.