Alcohol misuse is common in the UK Armed Forces (AF), with the prevalence higher in the AF than in the general population [1-4]. Research indicates that this trend continues after personnel leave service (veteran or ex-serving is used interchangeably in the UK) [1,5]. It has been estimated that more than 50% of those who have left the AF meet the criteria for hazardous alcohol use, a score of 8 or above on the Alcohol Use Disorders Identification Test (AUDIT) [3,6].

Research has shown that individuals in the general population underestimate their drinking and do not perceive it as problematic, even at potentially harmful levels [7]. Young males are at particular risk of underestimating their drinking [7]. This pattern is similar among the UK AF, with less than half of UK AF hazardous drinkers recognizing that they have an alcohol problem [8]. There is also a culture of heavy alcohol use in the UK AF, which is encouraged by the social environment and carries on after personnel leave service [4,9,10]. Therefore, leaving service could provide an opportunity to initiate behavior change in settings with less peer pressure to conform to social norms and promote alcohol awareness.

Focusing on personnel who have left service, a similar pattern has emerged for those who are seeking support for mental health problems and consume alcohol to cope. A recent study of treatment-seeking UK service leavers identified that 43% of respondents reported misusing alcohol and that alcohol misuse was commonly comorbid with posttraumatic stress disorder (PTSD) and common mental health difficulties such as anxiety and depression [11]. Alcohol misuse can also have an impact on treatment adherence. Treatment-seeking veterans with alcohol misuse attended fewer mental health appointments and were more likely to have a negative perception of mental health treatment when alcohol misuse is comorbid with depression or PTSD [12]. It is, therefore, important to develop interventions that may target drinking to cope with motivations, which may subsequently enhance engagement with mental health services and improve mental health outcomes.

The impact of alcohol misuse by AF personnel on the wider society (eg, health care utilization, productivity, and welfare) is unknown; however, it is likely to be increased compared with the general population. Research has indicated that heavy drinking in England, which is frequently comorbid with mental health difficulties [13], is estimated to cost the National Health Service (NHS) of the UK £3.5 billion (US $4.4 billion) per year (3.6% of its annual budget) [14].

There is a range of effective intervention options for management and treatment of alcohol misuse categorized as brief interventions, specialist treatment, and less intensive treatments that span the two [15]. Personnel of the UK AF who have left service typically access the same health care system as the general public, and the same interventions are offered to both groups.

Brief interventions for alcohol misuse are a popular management and treatment option used in the UK general population, often provided to individuals scoring 15 or below on the AUDIT [16]. A common theme among these interventions is the goal of improving recognition, targeting the individual’s motivations to reduce their alcohol consumption, and developing coping strategies to control and reduce intake [15-17]. This includes motivational interviewing, cognitive behavioral therapy, behavior self-control training, behavior change, and coping development, all of which are often tailored to the individual by a clinician [15].

Brief interventions aim to raise awareness of the risks associated with alcohol misuse and help individuals reduce their hazardous drinking. Often brief interventions are delivered to individuals who are not seeking help for alcohol misuse from a specialist alcohol service and are delivered in the general community setting (eg, general practitioners, hospital doctors, and nurses). There is a body of research that confirms the efficacy of brief interventions in reducing alcohol consumption and alcohol-related harm for those drinking at a hazardous level in the general population [18-20]. However, little is known about their efficacy in the AF context [19]. Given the shared culture in the military in which alcohol plays a meaningful role, it is important to evaluate the efficacy of brief interventions in this type of population.

The last two decades have seen a proliferation in the use of digital technologies to support brief intervention management and treatment of alcohol misuse in the general public; however, little attention has been paid to the AF community [21-24]. In the late 1990s, interventions were commonly delivered via a computer using CD-ROM–based programs. However, with the advent of the World Wide Web, many new opportunities arose to harness increased reach, provide real-time monitoring, and offer personalized treatment [25-31]. This includes the use of SMS, which has been shown to be effective in encouraging people to change their behavior [32-34].

Over the last 5 years, the mode of intervention delivery has shifted from web- to smartphone-based [35]. Smartphone interventions for alcohol misuse, such as Drink Less [24] and Drink Aware [36], have several advantages over web-based interventions. These include having a low cost per use, allowing for rapid changes and iterative development, avoiding the stigma associated with receiving help in person, and are highly convenient because they can be used as and when the individual wants (discreetly or openly). However, these smartphone interventions are focused on the general population and do not target individual beliefs, prevailing social contexts, and perceptions of consumption experienced by the AF community [9,37]. Smartphone-based interventions allow users to revisit information about their drinking habits as often as they need to and, thus, have the potential to promote positive behavioral changes [18,38]. Furthermore, there are indications of the potential of smartphone-based interventions being cost effective if found to be efficacious [25,28,29].

Most existing alcohol apps targeted at the general public include self-monitoring (eg, Drink Less [24], Drink Aware [36], and One You Drinks Tracker [39]), whereby users are encouraged to regularly record and monitor (via visual graphics) their alcohol consumption within an app [24,40]. Self-monitoring (or self-recording) has been found to be associated with improved outcomes and an effective behavior change technique (BCT) for reducing alcohol use. A BCT is defined as a specific component of an intervention designed to change behavior and a putative active ingredient in an intervention [21]. A review of personalized digital interventions for reducing hazardous and harmful alcohol consumption found that providing behavior substitution, problem solving, and providing a credible source were associated with better outcomes, including reductions in alcohol consumption [41]. There are benefits to the use of digital technology for the UK AF community. However, to date, there is no published work that seeks to test a brief intervention alcohol reduction app that is personalized to individual users or targeted to support military veterans.

The aim of this randomized controlled trial (RCT) is to assess the efficacy of a 28-day brief alcohol intervention delivered via a smartphone app (Drinks:Ration) in reducing self-reported weekly alcohol consumption between baseline and 3-month follow-up (day 84) among veterans who drink at a hazardous or harmful level and receive or have received support for mental health symptoms in a clinical setting.

This study was approved by the local ethics committee of King’s College London (registration number: HR-19/20-17438) and registered as a clinical trial (registration number: NCT04494594).

This is a two-arm participant-blinded (single-blinded) RCT, which compares a smartphone app (control arm) that includes feedback on baseline self-reported alcohol consumption with a smartphone app (intervention arm) that includes individualized normative feedback, in addition to features designed to enhance participants’ motivation, app interactive feedback, and self-efficacy in modifying their alcohol consumption. We hypothesize that the intervention arm app will be efficacious in reducing alcohol consumption compared with the control arm app. In this study, both the control and intervention arms will be delivered via one smartphone app known as Drinks:Ration. Participants in the control arm are given access only to the alcohol consumption feedback on the basis of publicly available health guidance [42] and reminder messaging to consult the feedback. Those in the intervention arm are given full access to the app, which includes all theoretically driven components and messaging (discussed further in the Intervention section). Both arms will be asked to use the app for 28 days. This study is designed such that the control arm structurally resembles the intervention arm but lacks the active ingredients (eg, drinks diary, interactive drinking feedback, and goal setting). This approach was selected to ensure (1) that both groups receive a digital intervention, (2) uniformity and provide relevance to real-world interventions, and (3) that participants are blinded from the study arm they are assigned to. The trial is conducted via the Drinks:Ration platform without any need for involvement of the research team, including the collection of informed consent and data collection. The study flow and data collection points are shown in Figure 1.

Participants may have been, or are presently, receiving treatment through Combat Stress. Treatment offered via Combat Stress is for depression, anxiety, and PTSD. However, Combat Stress does not offer alcohol treatment services. The eligibility criteria are as follows:

This study will recruit participants through Combat Stress (established in 1919), a third-sector charitable organization that provides mental health services, including substance misuse to UK veterans. It is the largest military charity in the United Kingdom in terms of the number of individuals treated, providing both inpatient and outpatient secondary mental health services to veterans and specializing in PTSD. Since 2011, Combat Stress has been funded by the NHS in the United Kingdom to provide a national specialist PTSD clinical service for veterans [48]. Combat Stress facilitates access to eligible participants and jointly with King’s College London oversees any risks that arise as a result of participation in the study. It is important to note that although this study uses a sample of veterans from Combat Stress, it is hoped that Drinks:Ration will be useful for the wider veteran community.

Potential participant contact details (postal address and/or email if available) will be extracted from the Combat Stress Patient Management System for those who meet the study eligibility criteria and who have provided consent to be contacted for research purposes. Only those who have had contact with Combat Stress over a 2-year period between January 1, 2018, and December 31, 2019, will be contacted. It is estimated that about 3000 patients with Combat Stress are eligible to be contacted by the research team.

Where contact details are available, eligible participants will be invited to take part via email in the first instance. The first contact will include an explanation of the study, link to the participant information sheet, and instructions on how to download Drinks:Ration using a unique quick response (QR) code. Once participants have downloaded the app, they will be invited to report alcohol consumption using TLFB for alcohol consumption [43] for the last 7 days and confirm the military serving status (to validate eligibility). Those meeting the study eligibility criteria will be invited to register an account and complete the baseline questionnaire (day 0).

Randomization occurs when a QR code is generated and a unique proxy identifier and participant gender are assigned. At this point, participants are automatically randomized to receive the control or intervention arm (see the Intervention section) and are blinded. Block randomization of size 2 will be used to ensure equal gender distribution across both conditions. The randomization procedure is carried out automatically by the Drinks:Ration platform with no human involvement, except to provide a proxy identifier and gender. The research team will be blinded to the randomization of the participant, except for DL, who led the development and will manage the Drinks:Ration app throughout the study.

The Drinks:Ration app, formerly called InDEx [49-51], has been developed following the Medical Research Council Complex Intervention Guidelines and using co-design methodology. It has been developed by the King’s Centre for Military Health Research (at King’s College London) and the University of Liverpool, supported by experts in smartphone app development, epidemiology, addiction psychiatry, and military mental health. The app is designed to support veterans drinking at a hazardous or harmful level by providing bespoke advice and support over a 28-day period. The app is designed to enhance participants’ motivation and self-efficacy in modifying their alcohol consumption by means of BCT in the content displayed (Multimedia Appendix 1) and the messaging sent to participants. The iterative development process, theoretical framework, and feasibility trial have already been reported [49-51]. Briefly, Drinks:Ration has been developed and tested with the following 5 core modules:

The app is compatible with all modern iOS- and Android-supported devices, and no involvement of the research team is required for participant enrolment. Data is collected, managed, and processed using the Google Firebase server infrastructure in London, United Kingdom.

In this study, the intervention arm will receive the app with all functionalities, including push notifications and SMS text messaging. The control arm participants will have access to only the questionnaire and feedback module and will not receive any form of personalized messaging, except prompts to complete questionnaires and reminders to review alcohol consumption feedback (see the Message section for more information). Participants in both arms will complete additional questionnaires on their mood and general mental health when responding to the weekly questionnaires. These responses will be used to personalize the content of the app and push notifications and SMS text messaging delivered to the intervention arm only.

Participants in both arms will be asked to use the app for 28 days. After which, they can continue to use the app; however, they will not receive personalized messaging, and the data collected after this point will not be used in the analyses. However, participants will receive a reminder message on day 84 and day 168 to complete questionnaires.

In addition to the Drinks:Ration app, participants will receive personalized push notifications and SMS text messaging that provide prompts to use the drinks diary, complete questionnaires, suggest alternative behaviors, provide feedback on goals, and promote a healthy lifestyle. A bank of personalized messages (both for SMS text messages and push notifications) informed by 180 tailored messages developed previously (which are informed by the Health Action Process Approach framework and targeted toward specific BCTs) [49] will be used.

Drinks:Ration uses baseline and contiguous measurements (day 7/14/21) to inform the type of message a participant receives to provide an individual participant-centric approach. Baseline measurements are used to identify suitable messages, and as a participant engages with Drinks:Ration, continuous measurements, including questionnaires (baseline and weekly questionnaires) and the drinks diary, are used to reflect current behavior and attitude. The messages cover a wide range of topics to target beliefs and motivations, with the primary aim of increasing the participant’s awareness of their drinking habits and behaviors. The messages are divided into 3 categories:

A participant can receive a maximum of 20 messages over the 28-day period, with a maximum of 2 messages in a single day. The system automatically decides when a message should be sent and the mode of delivery (push notification or SMS text messaging). A list of targeted (generic) messages to be sent to participants is defined in Table 1; except the messages listed in this table, participants in the control arm will receive no other messages. Participants in both arms will receive a generic message designed to promote retention of the Drinks:Ration app to allow for follow-up data collection. This will be sent monthly.

A summary of the measures and data collection timepoints in this study are detailed in Table 2.

At the end of the follow-up period, a random selection of 20 participants (10 from each study arm) will be invited to take part in a 60-min debrief session. The aim of this is to understand more about their use and experience of the Drinks:Ration app. During the session, participants will be asked to share their views on acceptability and usability and what can be done to improve their experiences. This will be done via telephone and transcript generated and used for analysis. Participants taking part in the debrief session will have the opportunity to view and discuss their own data.

Informed consent will be sought from all participants via the Drinks:Ration app before the collection of any personal data, and they will be informed from the outset that they can withdraw from the study at any time. Individual optional consent (screenshots presented in Figure 2) will be sought for access to the GPS location, sending of push notifications, or SMS text messaging. In addition, to promote open science, consent will be sought from participants to share their data anonymously for research purposes. These data will be released upon completion of the study. Only the questionnaire response, remote measurement technology data, and alcohol consumption statistics will be shared. All data will be deidentified, and no personal data will be released. Participants can change optional consents at any time via the settings page of the app until analyses are performed at which point data will be extracted and analyzed.

Participants can withdraw from the study at any time within the Drinks:Ration app (Figure 3). Participants can choose to withdraw from the study but allow the research team to use the data or delete their account by contacting the research team. We anticipate several reasons for withdrawal from the study, such as:

In the event that participants choose to withdraw from the study, we will provide prompt for a reason as to why they are withdrawing; however, providing a reason will be optional. Participants will be asked to uninstall the Drinks:Ration app. All data, including those from withdrawn participants, except the anticipated rare request for their data to be deleted, will be included in the final analysis.

It is not expected that participation in this study will lead to an increase in alcohol consumption. Nevertheless, in an adverse event, defined in this study as participants reporting (via the drinks diary or during contact with the research team) that they have consumed more than 25 UK units of alcohol within a 24-hour period, participants will be contacted by the research team, which includes the clinicians (Dr Dominic Murphy, Clinical Psychologist, Head of Research, Combat Stress and Dr Cerisse Gunasinghe, Counseling Psychologist, King’s College London), to perform a clinical interview and risk assessment. If concerns remain, a signposting booklet to relevant charities will be provided to the participants. The study clinicians may register an adverse event and withdraw the participants from the study; however, any data collected before withdrawal will be used for analysis.

The research team will monitor incoming data to ensure that the app is functioning correctly. The research team will not contact participants outside automatic messaging of the app unless they reach out to the research team with queries, for example technical issues, or if they are unsure of how to perform a task with the app.

Additional data will be collected during this study for future research. Participants can opt out for additional data collection at any time.

Statistical analysis will be performed after completing the data-collection phase. No interim analysis will be undertaken. The threshold for statistical significance will be P=.05, and effect sizes will be reported. Descriptive statistics (eg, demographics and response rate) and independent sample t tests and chi-square tests will be carried out to explore and identify potential differences between the intervention and control arms at follow-up. An intention-to-treat method will be used for primary outcome analysis such that those who are lost to follow-up will be retained in the primary analysis. Multiple imputation will be performed to estimate missing data, where appropriate. The primary outcome analysis will examine whether there is a statistically significant difference between the intervention and control arms on change in self-reported TLFB UK units consumed (as stated earlier, a difference of 4 UK units will be considered meaningful). Repeated-measures mixed modeling analyses will be conducted to examine the primary hypothesis that those who receive the full functionality of Drinks:Ration will report a greater reduction in alcohol consumption compared with control participants from baseline to 3-month follow-up (day 84). For the secondary outcomes, changes in the AUDIT score and WHOQOL-BREF computed quality of adjusted life years will be assessed using repeated-measures mixed modeling. These analyses will be repeated to assess changes between baseline and 6-month follow-up and will serve as a secondary outcome to assess the longer-term impact of the intervention on participants. These analyses will be reported as secondary outcomes.

For process evaluation measures, app utilization will be assessed using descriptive statistics of frequency of engagement using a previously published procedure [62]. This will include the number of times the app is initialized (started when not running in the background), the average session duration (time spent using the app overall and for each page), the number of times a participant performs an interaction (synchronize data, add a drink, or add a message rating), and the number of weeks in which participants remain engaged with the app. Participant engagement is defined as having at least 3 interactions in a 7-day period, other than receiving push notifications or SMS text messages, and will be used as a proxy for usability. An independent sample analysis will be carried out to explore and identify differences between the intervention and control arms. Usability of Drinks:Ration will also be reported using descriptive statistics and thematic analysis of debrief sessions. Finally, analyses will be carried out to identify differences between the intervention and control arms in app experience (as measured by MAUQ). In the pursuit of open science, data and code syntax will be published alongside reporting of the trial. As this is a single-blinded RCT, an independent researcher (who will be blinded to allocation) will review all analyses and data before publication. This study will be reported following the Template for Intervention Description and Replication [63] and CONSORT (Consolidated Standards of Reporting Trials) checklist [64].