Aim: The aim of this study was to evaluate the effectiveness of recommending the Drink Less app for reducing alcohol consumption compared with usual digital care in the UK.

Methods: Two-arm, double-blind randomised controlled trial comparing the effectiveness of recommending the Drink Less app (intervention) compared with the NHS alcohol advice webpage (comparator). Increasing- and higher-risk drinkers (AUDIT≥8) in the UK were recruited online between July 2020 and March 2022 and were followed up after one, three and six months. The pre-registered primary outcome was self-reported weekly alcohol consumption at six months, adjusting for baseline consumption.

Findings: We randomly assigned 5,602 people to the Drink Less app (n=2,788) or comparator (n=2,814). The response rate at the six-month follow-up was 80% and 79% between groups, respectively. The primary analysis assuming non-responders were drinking at baseline levels of consumption, found a non-significant greater reduction of 0.98 units in weekly alcohol consumption at six-month follow-up (95%CI -2.67 to 0.70). The data were insensitive to detect the hypothesised effect (Bayes factor = 1.17). Data were not missing completely at random, indicated by differences in those responding and not responding to six-month follow-up in terms of education, occupation and income. The pre-registered sensitivity analysis using multiple imputation accounting for differences between those responding and non-responding, showed the Drink Less app resulted in a 2.00-unit greater weekly reduction at six-month follow-up compared with usual digital care (95%CI -3.76 to -0.24).

Interpretation: Recommending the Drink Less app appears effective in helping increasing- and higher-risk drinkers reduce their alcohol consumption.