Research has indicated that loot boxes are risky gaming components that could exacerbate Internet gaming disorder due to a link between loot box purchasing and gambling. We conducted a systematic review to identify the characteristics of people who purchase loot boxes with real money, focusing on the relationships (a) between loot boxes and gaming, (b) between loot boxes and gambling, and (c) between loot boxes and other variables.
In this study, we conducted a systematic review to identify the characteristics of people who purchase loot boxes using real money. Specifically, this review focused on the relationships between (a) loot boxes and gaming, (b) loot boxes and gambling, and (c) loot boxes and other variables. This study aimed to reveal the psychosocial characteristics of people who excessively purchase loot boxes and identify factors that may develop or buffer loot box use. The findings of the present study are expected to provide valuable information that could be used to update treatment elements for Internet gaming disorder by incorporating treatment/prevention components for excessive loot box purchases.
Studies included in the literature review met the following criteria: (1) written in English, (2) assessed a bivariate relationship between loot boxes and other variables, and (3) were published in a peer-reviewed journal. Articles that included microtransactions in which people purchased pre-specified valuable in-game items (e.g., resources, gear, or skins) to enhance gameplay were excluded, as these were not considered to be associated with the gambling-like characteristics of loot boxes.
For each reviewed study, data were independently extracted by two raters who had previously reviewed the initial 201 articles. They resolved inter-rater disagreements by discussing until they reached a consensus. We collected the following information from each study: author, country/nationality, sample characteristics, research design, index of loot boxes, other variables related to loot boxes, and main results about the loot boxes.
Furthermore, the results of a pairwise comparison showed the effects of problem gambling on loot box spending (low-risk gamblers vs. non-problem gamblers: d = .429, moderate-risk gamblers vs. non-problem gamblers: d = .568, and problem gamblers vs. non-problem gamblers: d = .548) [11, 40]. In relation to a specific multiplayer game, Heroes of the Storm, which recently removed loot boxes from its online store, Zendle  conducted an analysis of players (n = 112) both before and after the loot box removal. The study showed that, after loot boxes were removed from the game, those who showed symptoms of gambling disorder appeared to spend significantly less money in-game compared with other groups. This finding indicated that those with gambling disorder symptoms spent more money in-game on loot boxes than any other player group.
Regarding motivations for purchasing loot boxes, Zendle et al.  identified the following reasons as to why gamers may buy loot boxes: to gain gameplay advantages (21.9%), gain specific items and characters and create a collection (19.2%), and experience the fun, excitement, and thrills of opening the loot box itself (16.0%).
The present study conducted a review of the literature to clarify the characteristics of people who purchase loot boxes with real money and identify factors that may encourage or buffer loot box spending. Specifically, for characteristics of people purchasing loot boxes, this review focused on the relationships between (a) loot boxes and gaming, (b) loot boxes and gambling, and (c) loot boxes and other variables.
In this review, it was noted that the relationship between eSports engagement and loot box purchasing was unexpectedly negative . Unlike general gaming, certain skills and techniques are required for eSports engagement. For example, according to a systematic literature review on the psychological aspects of eSports , eSports players try to be highly knowledgeable about the video game, think strategically and make fast and smart decisions, are motivated to keep moving forward (i.e., do not think about past performance), are able to separate daily life from performance, avoid being distracted and stay focused, cope adaptively with harassment, maintain a growth mindset (i.e., positive attitude), and warm-up before a performance, either physically or mentally. Furthermore, compared to recreational gamers, albeit eSports gamers were reported to have significantly higher average game times on weekdays and weekends, the latter had significantly lower psychological symptoms . In other words, the negative relationship between eSports gaming and loot box purchases may be due to eSports gamers playing games in a healthier manner than recreational gamers. In the future, it would be important to assess loot box use, and ways to prevent its problematic use, by identifying adaptive aspects and protective factors in professional gamblers and eSports players.
Fourteen of the 20 studies reported a positive relationship between loot boxes and gambling. Positive correlations were shown between high gambling severity and investment in, and engagement with, loot boxes; variables related to loot box use during gameplay (e.g., near-misses when buying loot boxes) mediated this relationship. Thus, loot box engagement was associated with not only symptoms of gambling disorder but also the interactions among these gambling symptoms and other game-related factors. In addition, one study showed a positive correlation between gambling-related cognitive distortions and risky loot box use . In treatment for gambling disorder, addressing cognitive distortions is an important component for reducing gambling disorder behaviors. Considering the gambling-like nature of loot boxes, a study remarked that cognitive distortions about loot boxes in the context of gaming may promote their excessive use . Therefore, if cognitive distortions about loot box engagement can be clarified and measured, the early detection of signs or behaviors leading to excessive loot box engagement could be used in the prevention and treatment of Internet gaming disorders.
In addition to gaming and gambling, the relationships among loot box engagement and other variables, such as mood, gender, physiological state, and motivation, have been examined. However, because there have been only a small number of studies on these variables in relation to loot box purchases and the findings have been inconsistent, we are unable to draw any conclusions about these relationships. Future studies should aim to identify the characteristics of people who excessively purchase loot boxes and identify factors that may contribute to or buffer this behavior.
First, we excluded studies that were not available in English. As high prevalence estimates of Internet gaming disorder have been found in Asia and North America and many studies on the topic might have been published in non-English language journals, this exclusion may be a limitation in this review . Second, although we identified the relationships between loot box engagement and gaming, gambling, and other variables, it remains unclear as to whether these relationships are common across game genres (e.g., massive multiplayer online role-playing games, puzzles) or limited to a specific genre. Thus, future research on trans-genre or nontrans-genre characteristics of loot boxes is needed. Third, we assessed the methodological quality of the included articles by the Quality Assessment Tool for Observational Cohort and Cross-Sectional Studies  and found that the methodological quality of the articles was relatively low. For example, all outcome measures in the 20 studies reviewed were self-report measures. To improve methodological quality, blinded assessors and logs of purchases and logins could be used, which would allow for more objective measurement. Furthermore, because undesirable responses might be given in online surveys (e.g., short time for answering the questionnaire), it is important to establish satisfactory measures as exclusion criteria.
When purchased, rather than received for free or as a skilled-play achievement, loot boxes are arguably a gambling product (Drummond, Sauer, Hall, Zendle, & Loudon, 2020). Money is risked based on a chance outcome for a prize of uncertain value (Devereux, 1979). Loot boxes bear an even closer functional relationship to gambling products when the prizes contained therein can be redeemed for cash (Drummond & Sauer, 2018). Some video game developers allow prizes to be sold back to the developer or sold to other players in a supported marketplace. Loot box prizes in other games can be sold on a third-party website, and some skins won in loot boxes can be used as a virtual currency for online gambling. In most cases entire game accounts, including prizes won from loot boxes, can be sold to others regardless of the intentions of the game developers.
Since loot boxes are available in many popular video games and structurally resemble traditional gambling games, there is a natural question whether these games are associated with gambling problems as a mental health condition and gambling harm as a public health issue. It is possible that children and/or adults recognise the similarity of loot boxes to gambling, and their use and enjoyment encourages interest in adult forms of traditional gambling. It is also possible that excessive spending on loot boxes can be a direct source of harm. Since video game loot boxes are a first experience of a gambling-related product for many young-people, it is necessary to understand how exposure to loot boxes relates to young-people's engagement and interest in traditional gambling. Past research has supported the notion that loot box use is more common in people with gambling problems (Brooks & Clark, 2019; Drummond, Sauer, Ferguson, & Hall, 2020; Kristiansen & Severin, 2020; Li, Mills, & Nower, 2019; Zendle & Cairns, 2018, 2019; Zendle et al., 2020; Zendle, Meyer, & Over, 2019). However, these studies have not attempted to use retrospective survey questions to understand if loot box use precedes gambling problems and harm (or potentially vice versa). The current study sought to remedy this deficit. The current study aimed to: 59ce067264