© The Author(s) 2020. The COVID-19 pandemic has brought about profound changes to social behaviour. While calls to identify mental health effects that may stem from these changes should be heeded, there is also a need to examine potential changes with respect to health behaviours. Media reports have signalled dramatic shifts in sleep, substance use, physical activity and diet, which may have subsequent downstream mental health consequences. We briefly discuss the interplay between health behaviours and mental health, and the possible changes in these areas resulting from anti-pandemic measures. We also highlight a call for greater research efforts to address the short and long-term consequences of changes to health behaviours.