Does providing a brief internet intervention for hazardous alcohol use to people seeking online help for depression reduce both alcohol use and depression symptoms among participants with these co-occurring disorders? Study protocol for a randomised controlled trial.

Introduction: Hazardous alcohol consumption is common among people experiencing depression, often acting to exacerbate depressive symptoms. While many people with these co-occurring disorders do not seek face-to-face treatment, they do seek help online. There are effective internet interventions that target hazardous alcohol consumption or depression separately but none that combine these online interventions without the involvement of a therapist. In order to realise the potential of internet interventions, we need to develop an evidence base supporting the efficacy of internet interventions for co-occurring depression and hazardous alcohol use without any therapist involvement. This study aims to evaluate the effects on drinking, and on depressive symptoms, of combining an internet intervention targeting hazardous alcohol consumption with one for depression.

Methods And Analysis: A double blinded, parallel group randomised controlled trial will be used. Participants with current depression who also drink in a hazardous fashion (n=986) will be recruited for a study to 'help improve an online intervention for depression'. Participants will be randomised either to receive an established online intervention for depression (MoodGYM) or to receive MoodGYM plus a brief internet intervention for hazardous alcohol consumption (Check Your Drinking; CYD). Participants will be contacted 3 and 6 months after receiving the interventions to assess changes in drinking and depression symptoms. It is predicted that participants receiving the CYD intervention in addition to MoodGYM will report greater postintervention reductions in alcohol consumption and depressive symptoms compared with those who received MoodGYM only. Hypothesised mediation and moderation effects will also be investigated. Using an intention-to-treat basis for the analyses, the hypotheses will be tested using a generalised linear hypothesis framework, and longitudinal analyses will use either generalised linear mixed modelling or generalised estimating equation approach where appropriate.

Ethics And Dissemination: This research comprises the crucial first steps in developing lower-cost and efficacious internet interventions for people suffering from depression who also drink in a hazardous fashion-promoting the widespread availability of care for those in need. This study has been approved by the standing ethics review committee of the Centre for Addiction and Mental Health, and findings will be disseminated in the form of at least one peer-reviewed article and presentations at conferences.

Trial Registration Number: NCT03421080; Pre-results.