## 2 Methodology  
We used a systematic review approach to find the existing groundwork on the use of IT in digital addiction research. A systematic review identifies, appraises, and synthesizes all the empirical evidence that meets pre-specified eligibility criteria to answer a given research question [32]. Systematic reviews employ a systematic and transparent process to define a research question, search for literature, assess literature quality, and synthesize findings qualitatively or quantitatively [33]. However, a systematic review never provides \"answers\". Systematic reviews only report as accurately as possible what is known and not known about the questions addressed in the review [34]. A systematic review has a set of core principles: (1) systematic/organized: a system or method that is designed to address the specific question is followed, (2) transparent/explicit: the method used in the review is explicitly stated, (3) replicable/updatable: the method used and the way it is reported can be repeated, repeated with modification, or updated by other researchers, and (4) synthesize/summarize: systematic reviews pull together the results in a structured and organized way [34]. The review protocol used in this study follows the guidelines proposed by [PERSON] et al. [35; 36]. The guidelines include planning the review, conducting the review, and documenting the review (Figure 1). Phase 1, the planning phase, involves four main processes: (1) justifying the need for a systematic review, (2) specifying the research questions, (3) developing the protocol, and (4) validating the protocol. Process 1 and 2 justify the importance of this review. Research questions will guide the next search process. Therefore, it is important to define stable and properly formulated research questions. The specific and valid research questions will guide the entire review process, including the primary study selection, data extraction, and data synthesis process. We identify the following research questions to guide this study: (RQI) What IT is used in digital addiction research? (RQ2)How is IT used in digital addiction research? (RQ3) What are the research directions in the use of IT digital addiction research? The technical processes used to conduct and report the review will be defined and justified in the research protocol. Phase 2, conducting review, consists of five processes. The first process is to define the search strategy. In the search strategy, we determined the search strings to find the appropriate studies. The search strategy was started with determining the basic scope, which includes the specific sources of studies and the search strings that will be used for an automated search on electronic data sources. We used the Scopus database as the database source. The search covered the literature published from 2017 until 2020. The literature search for papers published in 2020 was executed until 17 September 2020. Therefore, the results were obtained as of that date. The strings were searched in the article title, abstract, and keywords sections of the literature held in the Scopus database. This initial step in the search process resulted in the identification of 1655 papers. The search strings used are: \"(TITLE-ABS-KEY (\"online addiction\" OR \"internet addiction\" OR \"problematic internet use\" OR \"game addiction\" OR \"excessive internet use\" OR \"social media addiction\" OR \"social media attachment\" OR \"SNS addiction\" OR \"digital addiction\" OR \"smartphone addiction\") AND TITLE-ABS-KEY (\"detect\" OR \"detection\" OR \"diagnose\" OR \"measure\" OR \"measurement\" OR \"prevent\" OR \"prevention\" OR \"intervene\" OR \"intervention\" OR \"combat\" OR \"treat\" OR \"treatment\" OR \"assess\" OR \"assessment\" OR \"test\")) AND DOCTYPE (ar OR cp) AND PUBYEAR > 2016 AND PUBYEAR < 2021 \"  
The next step was to specify the selection criteria. We selected the primary studies based on the exclusion and inclusion criteria. The study selection criteria were then applied to exclude irrelevant studies.