We recruited university students from 3 local universities using purposive sampling in HK and used semistructured, individual interviews. The eligibility criteria included (1) being a HK resident aged ≥18 years, (2) studying at a local university, (3) being able to communicate in Cantonese, (4) drinking alcohol at least monthly (ie, current drinker), and (4) using a smartphone with installed IM apps. Participants with a history of psychiatric disorders or those participating in any alcohol treatment program were excluded. We recruited participants through universities' mass emails, posters, and social media (eg, Instagram and Facebook) with embedded QR codes. The QR code directed the students to the baseline questionnaire. Eligible participants who filled out the baseline questionnaire were invited to participate in the individual interview. To increase heterogeneity, we selected participants of different sex, years of study, and drinking patterns at baseline. Recruitment ceased after achieving information redundancy (no new information emerged).

The study was approved by the institutional review board of the University of Hong Kong/Hospital Authority Hong Kong West Cluster (UW 19-103). Individual interviews were conducted in a confidential area. We obtained verbal and written informed consent from all participants before the interview began. The institutional review board also allowed secondary analysis without additional consent. This study strictly followed the Consolidated Criteria for Reporting Qualitative Research guidelines [14]. A coupon of HK $100 (US $12.8) was provided to the participants as an incentive.

We interviewed 20 university students from September to October 2019. Each interview lasted approximately 1 hour. All interviews were conducted in a meeting room at the University of Hong Kong. Participants completed a web-based baseline questionnaire on their sociodemographic and drinking characteristics before being invited for the interview.

A research nurse (SLC) conducted the individual interviews. Only the research nurse and interviewee were present throughout the interview. The discussion began with the interviewer asking the participants to describe their perception of drinking, cues of drinking, and previous quit attempts as opening questions. Following the interview guide (available in Multimedia Appendix 1), the interviewer asked open-ended questions (eg, “What do you think about using mobile instant messaging apps for giving drinking advice to university students?” and “What would strengthen your motivation to quit or reduce drinking?”). All interviews were conducted in Cantonese and audio-taped with participants' consent. A HK $100 (US $12.78) cash coupon was given to each participant as a study participation incentive. No repeated interviews were carried out.

The audio-taped interviews were transcribed verbatim. Interim analyses were performed after each interview to refine the interview questions for in-depth understanding. Two researchers (YCW and YPZ) analyzed the transcripts using thematic analysis [15]. The researchers first read all the transcripts to familiarize themselves with the data and generate initial thoughts on the data. All the passages referred to the research question were coded, and codes that shared similar meanings were grouped into subcategories. The codes were then reviewed and organized into themes. Disagreements in coding were resolved through discussion with an additional researcher (MPW), who further reviewed and verified the consistency of the coding [16]. Interview data and coding were managed using NVivo (version 12; QSR International). Selected interview excerpts were translated into English and back-translated by researchers who are bilinguals for reporting. Information redundancy for data analysis was achieved at 20 participants as no new information was identified.

Rigor was assured by following the systematic and step-by-step process of thematic analysis guidelines strictly [16]. Data collection and analysis stages were undertaken concurrently, and an interim analysis was performed after each interview to ensure that the developing themes were grounded in the original data [16].

Table 1 shows that most participants were female (13/20, 65%), studying in their first to third year of university (13/20, 65%), had no previous quit attempt (11/20, 55%), and had no intention to quit (12/20, 60%). Further, 90% (18/20) and 85% (17/20) of participants received and sent more than 21 instant messages per day, respectively.

We identified 2 major themes from the data by thematic analysis. These included (1) the perceived important components of the IM intervention for alcohol reduction and (2) suggestions for designing the proposed IM intervention.

Participants considered using an IM app as a feasible and acceptable platform for providing alcohol reduction intervention. They preferred an IM app to other platforms (eg, email, Facebook, and Instagram) as it allowed for real-time interaction with the counselor and was able to provide drinking advice when needed.

We further identified 4 subthemes on the type of messages that the participants wish to receive. They preferred to receive instant messages based on personalized problem-solving, providing drinking consequences with credible sources, providing psychosocial support in time, and setting drinking goals with participants.

Participants perceived IM apps as a useful platform to obtain information about quitting and to inquire about personalized drinking advice when needed.

The importance of providing in-time drinking advice was further highlighted by the participants.

Regular receipt of messages related to negative consequences of drinking was considered by participants as a persuasive motivation to quit drinking. They indicated that these messages would create a daunting effect and encourage them to monitor their drinking amount.

Participants considered drinking a way to cope with stress, such as academic pressure. They would appreciate if the counselor could provide timely psychological support via an IM app to facilitate their quitting process.

Participants further suggested that simple messages, such as appreciating the effort of quitting, will motivate them to stay on the right track.

Participants highlighted the importance of having a sense of achievement from quitting. They suggested that the counselor personalize the objective and monitor each participant's progress regularly, which can strengthen their commitment to quitting.

Participants provided suggestions on the designs and methods for delivering the proposed intervention. These suggestions included (1) optimal text length and delivery frequency, (2) adding interesting elements in the chat, and (3) peer as a counselor.

When asked about the design of the intervention, participants proposed that the messages should be simple and concise. They also preferred not to receive messages every day. They referred lengthy and frequent messages as aversive and not necessary.

Participants further suggested sending the messages specifically on weekends as they may have more time to drink.

Participants preferred adding more personalized emojis or stickers in the chat, which would create a more casual and closer relationship with the counselor. Some recommended adding specific emojis relevant to the texts, and they described these messages as more noticeable.

Other participants preferred to receive pictures or animation besides written language. They believed the media would be a convincing way to reinforce the idea of quitting.

Some participants suggested that having a peer as a counselor to give drinking advice would help strengthen the intervention. They believed that peers could better understand their drinking history and empathize with their challenges while quitting.

This study explored the perceptions of using IM apps for alcohol reduction intervention in Hong Kong university students who speak Chinese or are of Chinese origin. Participants considered an IM app as a feasible and acceptable platform for delivering drinking advice. Based on their preference, they preferred to receive IMs based on personalized problem-solving (eg, identify ways to stop drinking), drinking consequences with credible sources (eg, provide scientific evidence on the harm of drinking), in-time psychosocial support (eg, address emotional needs promptly), and goal setting to reduce drinking (eg, personalized drinking goals) [17]. They also provided suggestions on the designs of the proposed intervention, which further improved its acceptability and feasibility.

Participants considered the ability to provide in-time drinking advice to them as one of the primary merits of using IM apps. A similar finding was obtained in another formative study of developing a text messaging–based intervention for alcohol reduction in the United States [18]. Evidence suggested that immediate informational and psychological support were important to enhance confidence to quit drinking; it facilitated quitting by helping the drinkers tackle challenges in time and promoted their motivation to quit [19]. In addition, clinical consultation with health care professionals was limited by time constraints and sometimes could be very brief. By using IM apps, counselors can learn about their quitting process regularly, tailor specific interventions that suit their drinking characteristics, and facilitate quitting more effectively.

Apart from addressing personal needs, the ability to provide credible information on the harm of drinking was regarded by participants as a crucial motivator to reduce drinking. Unlike mobile health trials of smoking cessation, smokers preferred receiving gain-framed messages (eg, benefits of quitting smoking) to loss-framed messages (eg, harm of smoking) as they were already aware of the harm of smoking [20]. Emerging research showed that drinkers had misconceptions about alcohol use and considered it beneficial to health (eg, drinking low to moderate red wine can reduce the risk of cardiovascular diseases) [21]. Providing credible information on drinking harm clarifies their fallacy of alcohol and promotes their motivation to quit.

Participants emphasized the importance of receiving emotional support from the counselor during the process of quitting when using IM apps. A study showed that in-time person-to-person psychosocial support was one of the important factors for successful quitting in substance use treatment, as sustained external emotional support was a key mediator for achieving long-term abstinence [22]. By using IM apps, counselors can determine drinkers' emotional responses to relapse while quitting and promptly tailor the appropriate intervention to address their emotional needs [22]. Compared with traditional text-based interventions (eg, SMS text messaging), the proposed intervention allows real-time interaction with the counselor and facilitates better quitting outcomes by enhancing drinkers' psychosocial supports.

Apart from using IM apps for providing alcohol reduction intervention, the proposed intervention may also inform the design of similar interventions for treating other adverse health behaviors, including using IM apps for substance use treatment. The IM intervention would need counselors to deliver a chat messaging intervention to participants, which may incur higher operational costs than conventional text messaging–based interventions. Nevertheless, as mobile IM apps are freely available in the market and are widely used by the general population, and artificial intelligence–based technologies are becoming more advanced and mature, the development of chatbots would reduce the operational cost of IM interventions in the future [23].

This study has some limitations. First, as it focused on using IM apps for alcohol reduction intervention, non–smartphone owners were excluded. The views expressed during the interview were specific to university student drinkers who own a smartphone; they are typically younger and have higher digital literacy than the general population [13]. Second, the representativeness of the study was limited as participants were recruited from universities in Hong Kong, and over half of the participants (60%) had no intention to quit drinking; hence, our findings may not be generalizable to non-Chinese university students and people who have the intention to quit or reduce drinking. Third, member checking was not conducted due to lack of funding; we improved the trustworthiness of the findings by having 2 researchers independently code the transcripts and an additional investigator to further verify the consistency and accuracy of the coding.

This formative study has informed the designs and contents of an IM intervention for alcohol reduction in university student drinkers. It provides an alternative to traditional SMS text messaging–based intervention. The proposed intervention will be evaluated in a randomized controlled trial with Hong Kong university settings (NCT04025151).