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Problematic Online Buying-Shopping: Is it Time to Considering the Concept of an Online Subtype of Compulsive Buying-Shopping Disorder or a Specific Internet-Use Disorder?

Problematic online buying-shopping became a recent research topic, and the question arises as to whether it would be useful to differentiate between a “predominantly online” and a “predominantly offline” compulsive buying-shopping disorder (CBSD) subtype by analogy with gaming disorder and gambling disorder in the ICD-11. This narrative review aims at reflecting the discussions on overlaps of problematic online buying-shopping with both offline CBSD and specific internet-use disorders. Preliminary data suggest that problematic online buying-shopping shares many commonalities with both offline CBSD and potential specific internet-use disorders (e.g., gaming disorder, pornography-use disorder, or social-network–use disorder). However, there is a lack of research addressing the etiology, underlying affective and cognitive mechanisms, psychosocial correlates, comorbidity profiles, and treatment of problematic online buying-shopping. The question of whether online CBSD can develop independently from offline CBSD or only as medial transformation of offline CBSD still remains unanswered due to limited research on problematic online buying-shopping. Both perspectives are conceivable: that online CBSD represents a standalone specific internet-use disorder or the online subtype of CBSD. Future studies should examine which approach has clinical utility and indicates specific treatment options and better outcomes.


Introduction
Clinical interest in the phenomenon of excessive, maladaptive consumption of consumer goods emerged already in the early twentieth century [1]. Since then, research efforts have gradually increased to investigate the phenomenology, assessment, prevalence, psychosocial correlates, neuropsychology, and treatment of this mental health condition [2-6, 7•]. Although compulsive buying-shopping disorder (CBSD) is not listed as a separate mental disorder in the ICD-11, it is now mentioned as an example of the "other specified impulse control disorders (6C7Y)" category [8]. Some authors argue that it would fit better into the category of "other specified disorders due to addictive behaviors (6C5Y)" [9•]. These considerations refer to the overlaps of CBSD with substance-related and behavioral addictions regarding phenomenology and proposed underlying mechanisms (e.g., diminished control over the activity, cue-induced craving responses, gratification and compensation processes, continuation of the activity despite negative consequences) [2, 3, 9•, 10, 11].
Buying-shopping patterns have changed with the increase of the e-commerce marketplace and the development of Web 2.0 technologies over the last 20 years [12]. The e-marketplace offers many opportunities for efficient goal-directed information search, price comparisons, und convenient purchasing of a huge variety of products. Many consumers engage in both offline and online buying-shopping, and some strongly prefer online buying-shopping. Research suggests that a subgroup of online customers is likely to develop online CBSD [13,14]. Initial studies that specifically addressed online CBSD have been conducted more than 15 years ago [15][16][17]. Data from a German clinical sample (n = 122) showed that one-third of patients with CBSD reported excessive buying-shopping on the internet, which was related to higher severity of CBSD [18••]. Selfreports of Parisian university students (n = 200) indicated a prevalence of online CBSD of 16% [19]. In this context, online CBSD became a recent research topic [20,21], and the question arises as to whether it would be useful to differentiate between a "predominantly online" and a "predominantly offline" CBSD subtype by analogy with gaming disorder and gambling disorder in the ICD-11 [8].
Recently, a Delphi study was conducted among international experts in the field of CBSD in order to develop potential diagnostic criteria for CBSD [7•]. Considering the migration of traditional offline CBSD to the online retail market, experts were asked whether the diagnostic criteria should include a specifier "predominantly offline vs. predominantly online" CBSD. Interestingly, they did not consent on such a specifier [7•]. The study did not explore why the experts decided against the specifier. However, various reasons for the rejection would be conceivable. Experts may not have detected any substantial differences between online and offline CBSD in their clients and argue that the specifier does not add anything useful to the diagnosis. Moreover, due to the scarcity of literature about the systematic comparison between online and offline CBSD, they may have not been aware of any research data that may justify such a specifier.
In our opinion, it is worth reflecting on whether an online subtype of CBSD may have specific clinical implications. An alternative view would be to understand online CBSD as a specific internet-use disorder because it occurs only on the internet. Below, we will take a closer look at both perspectives and will address potential commonalities of online CBSD with offline CBSD or specific internet-use disorders.

Same-Same: Online CBSD and Offline CBSD
CBSD on the internet shares several key features with offline CBSD (Table 1). These include in the first place diminished control over the acquisition of consumer goods without utilizing them for their intended purposes [7•, 22, 23]. Online and offline CBSD are associated with spending much time thinking about buying and shopping (preoccupation) and increasing priority given to these activities. The maladaptive offline/online behavior results in clinically significant distress (e.g., shame, embarrassment, regret, anxiety, depressive symptoms) and/or impairment in different areas of functioning (e.g., indebtedness, familial discord, jeopardizing relationships and career opportunities), and it is continued or even escalated despite the occurrence of those negative consequences [7•, 22, 23]. Similar to offline CBSD [6,10,24], individuals with online CBSD show craving responses towards buying/shoppingrelated visual cues [10, 11, 14, 25••]. The maladaptive online as well as offline buying-shopping activities serve to experience pleasure (gratification) or to compensate negative feelings [26][27][28]. Research suggests common vulnerability factors for online and offline CBSD, in particular, strong materialistic values, low self-esteem, and identity confusion [15,[27][28][29][30][31][32]. It appears that both CBSD modes serve to cope with materialistic and narcissistic needs and to escape reality.
It is important to consider certain advantages of the e-marketplace (e.g., shopping in public transport via smartphone, personalized advertisements, easy credit payment systems) that contribute to specific phenomenological characteristics of online CBSD. Frequent, time-consuming, excessive browsing through shopping websites with or without purchasing anything is very typical for online CBSD. Although extensive "window shopping" may also occur in offline CBSD, it is physically impossible to visit a similar number of stores in the offline environment as on the internet in a comparable amount of time. Individuals with online CBSD may not purchase anything on the internet for several reasons, e.g., they try to reduce their money expenses, made progress in therapy, promised stopping overspending to their relatives, have accumulated debts, due to pending court proceedings, or their accounts were locked because of unpaid invoices. Most reasons do not differ from reasons to cut down offline CBSD. However, individuals with online CBSD may also experience reward while spending several hours a day or during nights searching for goods on the internet [33]. This means that individuals with the predisposition for CBSD (i.e., high materialistic values, low self-esteem, identity confusion) may prefer online buying-shopping if they have the expectancy that browsing shopping sites is associated with the prompt experience of pleasure or relief from discomfort [34]. Such time-consuming browsing can crowd out other social, familial, or occupational activities. Affected persons are not protected from online CBSD episodes at work (where they may order goods on the internet via smartphone). Clinically, extensive browsing shopping websites (with simultaneous reduction/absence of online purchasing) should not be overlooked in online CBSD as per the way that dietary restriction behaviors (with simultaneous reduction/absence of compensatory behaviors such as self-induced vomiting) are important to assess, for example, in patients with bulimia nervosa [35].

Same-Same: Online CBSD and Specific Internet-Use Disorders
Online CBSD has also a lot in common with (potential) specific internet-use disorders, e.g., gaming disorder, pornography-use disorder, or social-network-use disorder (Table 1). This includes, for example, the diminished control over the use of certain internet sites (i.e., shopping sites) and the increasing priority given to the use of this first-choice internet application (for online CBSD: browsing shopping sites, searching for product information, making orders) [22,34]. Similar to other specific internetuse disorders, maladaptive excessive online buying-shopping activities are continued or escalated despite negative consequences (e.g., clinical significant distress, psychosocial problems, indebtedness, impairment in important areas of functioning).
With regard to affective aspects, cue-induced craving responses towards application-specific cues have been found in several internet-use disorders [34,36,37] and also in individuals with a propensity for online CBSD [14, 25••]. Similar to other specific internet-use disorders [34,38,39], in online CBSD the use of shopping sites results in the quick experience of positive feelings (gratification) or relief from negative feelings (compensation) and is motivated by the anticipation of such benefits. Using motives further include the expectancy to search for infinite product information, find an immense variety of products, browse and purchase unobserved (anonymity), avoid social interactions during buying-shopping, satisfy the urge to shop promptly, regulate emotions immediately, and mitigate identity confusion quickly [14][15][16][17]28].
There are various parallels between online CBSD and other internet-use disorders. The triple-A-engine for online pornography-use disorder (i.e., accessibility, affordability, anonymity) [40] could also be used to describe internetspecific aspects that accelerate the development and maintenance of online CBSD. Of interest are also the connections of online CBSD with social-network-use disorder [41][42][43][44]. In college students from Singapore (n = 1110), those participants who were at-risk for social-network-use disorder were also at risk for online CBSD [44]. The relationship between problematic social-network use and the risk for online CBSD in a Chinese convenience sample (n = 1109) was mediated by financial social comparison and materialism [42]. Buying-shopping and communicating on the internet are popular behaviors often connected via in-app shopping advertisements on social networks. A bidirectional relationship between the two (potential) disorders is possible. Communicating about products via social networks may generate excitement and may also trigger cue reactivity and craving as well as social comparisons with other customers and accentuate the tendency towards materialism and CBSD, and vice versa [16,42]. In addition to these rather environmental aspects, there might be common vulnerability factors for social-network-use disorder and online CBSD such as social anxiety, narcissistic traits, and identity confusion [31,43,[45][46][47].

Conclusions
Online CBSD shares many commonalities with both offline CBSD and specific internet-use disorders, whereas the overlaps are probably not exhaustive. Distinguishing between a "predominantly offline" and a "predominantly online" subtype of CBSD would be consistent with the ICD-11 subtyping approach for gaming and gambling disorders [8]. However, this approach has been debated even in the context of gaming disorder [48]. It is questionable of whether splitting CBSD into an offline and online subtype will still be valuable in the near future. In the course of the increasing digitalization of everyday life and further expansion of the e-commerce marketplace, differentiating between online and offline CBSD may be superfluous because online buying-shopping may become the preferred mode for almost everyone. Then, online and offline buying-shopping could be so intertwined that it may no longer make sense to distinguish between them.
An alternative view would be to understand online CBSD as a specific internet-use disorder. Many of the phenomenological features (e.g., time-consuming browsing) and mechanisms (e.g., internet using motives) of online CBSD may suggest such a categorization [14,17,34]. One important question is whether online CBSD can develop independently from offline CBSD or only as a medial transformation of offline CBSD into online CBSD. Both perspectives are conceivable: that online CBSD represents a standalone specific internet-use disorder or the online subtype of CBSD. However, until more is known about the etiology, underlying affective and cognitive mechanisms, psychosocial correlates, comorbidity profiles, and treatment of online CBSD, the question still remains unanswered. Future research should examine which approach may have clinical utility and indicates specific treatment options and better outcomes: a categorization within CBSD ("predominantly online CBSD" and "predominantly offline CBSD") or within the group of specific internet-use disorders. Moreover, future studies should shed more light on common vulnerability and shared underlying affective and cognitive mechanisms of online CBSD and social-network-use disorder (and maybe other specific internet-use disorders), resulting in possible transdiagnostic interventions. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/.