Evaluating the quality of evidence for gaming
disorder: A summary of systematic reviews of
associations between gaming disorder and
depression or anxiety
Michelle Colder CarrasID
*, Jing Shi
, Gregory HardID
, Ian J. Saldanha
1Behavioral Sciences Institute, Radboud University, Nijmegen, Netherlands, 2Institute for Mental Health
Policy Research, Centre for Addiction and Mental Health, Toronto, Ontario, Canada, 3School of
Rehabilitation Science, Faculty of Health Sciences, McMaster University, Hamilton, Ontario, Canada, 4MGH
Institute of Health Professions, Mass General Brigham, Boston, Massachusetts, United States of America,
5Center for Evidence Synthesis in Health, Department of Health Services, Policy, and Practice, and
Department of Epidemiology, Brown University School of Public Health, Providence, Rhode Island, United
States of America
¤Current address: International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore,
Maryland, United States of America
Gaming disorder has been described as an urgent public health problem and has garnered
many systematic reviews of its associations with other health conditions. However, review
methodology can contribute to bias in the conclusions, leading to research, policy, and
patient care that are not truly evidence-based. This study followed a pre-registered protocol
(PROSPERO 2018 CRD42018090651) with the objective of identifying reliable and method-
ologically-rigorous systematic reviews that examine the associations between gaming disor-
der and depression or anxiety in any population. We searched PubMed and PsycInfo for
published systematic reviews and the gray literature for unpublished systematic reviews as
of June 24, 2020. Reviews were classified as reliable according to several quality criteria,
such as whether they conducted a risk of bias assessment of studies and whether they
clearly described how outcomes from each study were selected. We assessed possible
selective outcome reporting among the reviews. Seven reviews that included a total of 196
studies met inclusion criteria. The overall number of participants was not calculable because
not all reviews reported these data. All reviews specified eligibility criteria for studies, but not
for outcomes within studies. Only one review assessed risk of bias. Evidence of selective
outcome reporting was found in all reviews—only one review incorporated any of the null
findings from studies it included. Thus, none were classified as reliable according to pre-
specified quality criteria. Systematic reviews related to gaming disorder do not meet meth-
odological standards. As clinical and policy decisions are heavily reliant on reliable,
accurate, and unbiased evidence synthesis; researchers, clinicians, and policymakers
should consider the implications of selective outcome reporting. Limitations of the current
summary include using counts of associations and restricting to systematic reviews pub-
lished in English. Systematic reviewers should follow established guidelines for review
PLOS ONE | https://doi.org/10.1371/journal.pone.0240032 October 26, 2020 1 / 21
Citation: Colder Carras M, Shi J, Hard G, Saldanha
IJ (2020) Evaluating the quality of evidence for
gaming disorder: A summary of systematic
reviews of associations between gaming disorder
and depression or anxiety. PLoS ONE 15(10):
Editor: Florian Naudet, University of Rennes 1,
Received: November 27, 2019
Accepted: September 18, 2020
Published: October 26, 2020
Peer Review History: PLOS recognizes the
benefits of transparency in the peer review
process; therefore, we enable the publication of
all of the content of peer review and author
responses alongside final, published articles. The
editorial history of this article is available here:
Copyright: ©2020 Colder Carras et al. This is an
open access article distributed under the terms of
the Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the manuscript and its Supporting
conduct and transparent reporting to ensure evidence about technology use disorders is
Gaming disorder or Internet gaming disorder (IGD) is a disorder related to excessive video,
computer, or online game play that results in psychological distress and/or functional
impairment [1,2]. Internet gaming disorder was included as a condition for further research in
edition of the Diagnostic and Statistical Manual (DSM-5) and the diagnosis of gaming
disorder has been added to the 11
edition of the World Health Organization (WHO) Interna-
tional Classification of Diseases (ICD-11) [1,2]. Gaming disorder includes symptoms related
to substance use disorder, such as loss of control (that continues despite negative conse-
quences), functional impairment, distress, and/or interference with daily activities. The disor-
der is distinguished from other related disorders, such as technology overuse, Internet
addiction, and social networking addiction . Recent commentaries have described gaming
disorder (which we will define here broadly to include the diagnoses of IGD or gaming disor-
der, problematic/pathological video gaming, and other concepts related to excessive video
game play) as a clinical and public health problem in urgent need of advancements in treat-
ment development [4,5].
Delineation and measurement of a clear construct with no overlap with other related condi-
tions, such as gambling, Internet use, and technology use, are crucial to this field. Many recent
commentaries on the need for a diagnosis of gaming disorder use terms like “Internet addic-
tion or Gaming disorder” , “Internet-related disorders including gaming disorder” , and
“Internet addiction including gaming addiction” , pointing to the persistent overlap in mea-
surement of these problematic behaviors. From a public health perspective, many forms of
Internet use—not just gaming—continue to be recognized as potentially problematic, as evi-
denced by a recently-funded international research collaborative on problematic Internet use
Systematic reviews are research activities that follow established, rigorous methods to sum-
marize all relevant evidence on specific research questions that are vital for decision-making
by clinicians, patients, policy-makers, and other stakeholders. The methods include framing
the research question, searching for the evidence, screening studies for eligibility, assessing
risk of bias and extracting data from included studies, conducting qualitative and, where mer-
ited, quantitative syntheses, and reporting the findings. Recent decades have witnessed a surge
in the number of systematic reviews conducted . Multiple standards have been developed
for the conduct and reporting of systematic reviews . However, research has shown that
reviews in some fields provide low-quality evidence, are unreliable, and can be sources of bias
themselves [8,10,11]. Bias can sometimes be introduced due to methods used in the systematic
review (‘meta-bias’) .
One source of meta-bias can potentially occur when a given study included in a review
reports results for a given relevant outcome in multiple ways, and the reviewer must make a
choice among these to determine which result(s) to extract for the review [13,14]. In this situa-
tion, choice of the result based on the largest (or smallest) magnitude of treatment effect, on
statistical significance, and/or on the result that supports the reviewer’s conscious or subcon-
scious preconceptions can be problematic and lead to bias. Such bias can be preempted by
completely prespecifying the five elements of an outcome (Fig 1) [10,15]. However, complete
Evaluating the quality
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Funding: The author(s) received no specific
funding for this work.
Competing interests: I have read the journal’s
policy and the authors of this manuscript have the
following competing interests: Dr. Colder Carras
has spoken to the World Health Organization about
this topic at the request of the Entertainment
Software Association but has received no funding,
honorarium, fees, meals, lodging, donations or
reimbursement. She has also spoken about this
topic to other audiences: She received an
honorarium and airfare to speak to the Johns
Hopkins Department of Psychiatry about video
games and mental health and has addressed this
topic in other unpaid/unreimbursed conferences
and lectures. Dr. Colder Carras has no past,
current, or planned business or financial
relationships with any other organization related to
the video game industry. She has acted as a
consultant with a nonprofit organization, Stack Up,
that provides mental health and suicide prevention
support through online video game play. She is
currently a member of the American Association
for Suicidology Technology and Innovation
Committee and believes that video games and
social media have the potential to be useful
platforms for delivering public health interventions.
She sometimes plays video games herself. The
other authors declare no conflict of interest.
prespecification is not always possible and/or may be considered too restrictive. Moreover,
choosing specific results from multiple reported analyses from multiple data sources for a
given study is a multi-dimensional problem. In one study of meta-analytic methods, an exami-
nation of outcomes reported in 14 clinical trials revealed that, depending on which outcomes
from the trials were chosen by the reviewers, over 34 trillion meta-analyses were possible .
Now that gaming disorder has been recognized as a disorder by the WHO, ensuring sys-
tematic and accurate measurement of gaming disorder in studies and accurate reporting of
exposures, outcomes, and conclusions in reviews are vital for ongoing decision-making
regarding diagnosis, treatment, and public health interventions. Given the established associa-
tion between gaming disorder and two common mental health outcomes—depression and
anxiety—we limited the scope of our study to systematic reviews that included data about
these outcomes. This allowed us to explore the issue of selective outcome reporting in reviews.
In this summary of systematic reviews, we assess the reliability of current reviews that have
examined the association between gaming disorder and depression or between gaming disor-
der and anxiety in any population. We aimed to answer the following research questions to
inform directions for future research and policymaking:
1. Do systematic reviews of the associations between gaming disorder and depression and
between gaming disorder and anxiety meet reliability standards for systematic reviews?
Fig 1. Defining outcomes for a systematic review or meta-analysis. Elements of outcome domains required for
complete outcome specification in health research. Figure adapted from ; see also the PRISMA-P  statement or
description of PICOS .
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2. Do systematic reviews of the associations between gaming disorder and depression and
between gaming disorder and anxiety distinguish between gaming disorder and other con-
structs, such as Internet addiction?
3. Do systematic reviews of the associations between gaming disorder and depression and
between gaming disorder and anxiety report outcomes selectively?
4. What are the associations between gaming disorder and depression and between gaming
disorder and anxiety reported in reliable systematic reviews?
This study is a summary of systematic reviews of the associations between gaming disorder
and depression and between gaming disorder and anxiety in any population. The review meth-
ods, including the research question, search strategy, inclusion/exclusion criteria, and risk of
bias assessment, were developed a priori and described in the registered protocol (PROSPERO
2018 CRD42018090651); these are also available in S1 Protocol. All data, the protocol, a list of
articles excluded at the full-text screening stage with reasons for exclusion, and other support-
ing documentation are available on our Open Science Framework website (see Project on OSF
website) and in Supporting Information files. In this paper, we discuss two groups of research
studies: the systematic reviews (henceforth called ‘reviews’) and the primary studies included
in those reviews (henceforth called ‘studies’).
We examined reviews that included studies of the associations between the exposure of
gaming disorder (as defined by the review authors) and the outcomes of depression or anxiety.
We restricted to reviews published in English by June 24, 2020. We excluded reviews that:
• Were narrative reviews, overviews of reviews, commentaries, and other non-systematic
reviews of studies;
• Only examined Internet addiction or other technological addiction; or
• Did not report results for the associations between gaming disorder and depression or anxi-
ety separately (e.g., we excluded reviews that only reported pooled outcomes for "mental
Fig 2 illustrates how we defined the domains of depression and anxiety in our study. For
the outcome of depression, we restricted to scales, subscales, diagnosis, or clinical interviews
for depression or more severe single symptoms related to depression, such as suicidal ideation,
but excluded measurements of nonspecific symptoms, such as low energy, sleep problems, sad-
ness, or withdrawal from social activities. For the outcome of anxiety, we included scales, sub-
scales, diagnosis, or clinical interviews for anxiety, social anxiety, and social phobia, but
excluded measurements that combined anxiety with other constructs (e.g., anxiety/
Search strategy and screening process
We conducted electronic searches of PubMed and PsycInfo for published reviews and meta-
analyses (searches were current as of June 24, 2020). Searches combined terms related to gam-
ing disorder and terms related to depression or anxiety (S1 Search Strategies). In addition, we
reviewed all years of the Journal of Behavioral Addictions, including its supplements, and all
proceedings of the International Conference on Behavioral Addictions.
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Assessment of reliability of reviews
We adapted the definition of “reliability” of systematic reviews developed by Cochrane Eyes
and Vision [17–21]. This definition, in turn, was informed by items identified from the Critical
Appraisal Skills Programme (CASP), A Measurement Tool to Assess systematic Reviews
(AMSTAR), and the Preferred Reporting Items for Systematic Reviews and Meta-Analyses
(PRISMA) tools [9,22,23]. According to this definition, a review is reliable when its authors
did each of the following:
(1). Defined eligibility criteria for including studies;
(2). Conducted a comprehensive literature search for studies (i.e., searched at least one rele-
vant electronic database, such as PubMed and PsycInfo; used at least one other method of
searching, such as searching the grey literature, searching for unpublished studies, and
searching the reference lists of included articles; and were not limited to English language
(3). Assessed risk of bias in individual included studies;
(4). Used appropriate methods for meta-analysis, when conducted (e.g., adequately account-
ing for any heterogeneity); and
(5). Presented conclusions that were supported by the evidence reported in the review.
Because we also examined each study included in the reviews, we added an additional crite-
rion that review authors should have:
(6). Specified in the methods or protocol which outcomes from their eligible studies were
included in the synthesis or synthesized all reported outcomes from each included study.
Fig 2. Domains used to define depression and anxiety as constructs for analysis. YSR = Youth Self Report scale.
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We classified a review as reliable only if all six of the criteria were met. Finally, we con-
ducted a full assessment of the quality of the included reviews using A Measurement Tool to
Assess systematic Reviews—version 2 (AMSTAR 2) ; the full results of this assessment are
found in S1 Data Extraction.
Assessment of other outcomes
Other outcomes included the proportion of all studies within a review that measured gaming
disorder with a gaming disorder-specific instrument; the proportion of reviews that specified
all elements of an outcome; and the specific review- and study-level associations between gam-
ing disorder and depression and anxiety. All reported associations within the studies were
extracted from the original study reports and characterized as present and positive, present
and negative, present and null, unclear, or absent. The count and type (positive, null, negative,
unclear, or absent) of results for each study were compared with the results reported for each
study in the reviews. We also made several comparisons regarding overall conclusions about
the associations between gaming disorder and depression and between gaming disorder and
anxiety by comparing bivariable versus multivariable analyses, cross-sectional versus longitu-
dinal analyses, and results from reviews classified as reliable versus results from all reviews.
We developed and pilot tested a data extraction form using Microsoft Excel
, based on the
form developed by Mayo-Wilson et al. . We added questions relevant to reviews of epide-
miological studies . During the initial data extraction, we noticed discrepancies in how
specific studies were reported in the reviews, resulting in potential selective outcome reporting
at the review level. To ensure that we evaluated this potential source of bias, we expanded the
scope of our preregistered protocol to include examining study-level outcomes and how they
were reported in reviews.
Two investigators from among MCC, JS, and GH extracted data from each review, consult-
ing the third investigator for resolution of discrepancies where needed. If a review did not
have a summary of findings table that included the total number of studies mentioned in the
results or in supplementary material, we extracted data for all studies mentioned in text or
tables of the Results section. Data on depression and anxiety outcomes within each study of
each review were extracted by one investigator. Extracted data for a 10% random sample of
studies were validated by the second and third investigator.
Data extracted from the reviews included information on methods for specifying eligibility
criteria and outcomes, specific measurements (e.g., scales) of depression and anxiety in
included studies, analyses conducted, whether and how review authors assessed risk of bias in
included studies, specific measurement (e.g., scales) of gaming disorder in included studies,
and all items from the AMSTAR 2 tool.
We summarize below the three conditions that had to be met for a specific measurement or
scale to be classified as asssesing gaming disorder (Fig 3):
• The specific measurement or scale asked questions about computer, video, online, or digital
game use in general, rather than just a single game (e.g., World of Warcraft
• The specific measurement or scale asked questions about gaming or online gaming rather
than Internet or computer use in general (e.g., did not use only an Internet addiction mea-
sure, such as the Young Internet Addiction Test or the Compulsive Internet Use Test). If a
study mentioned adapting a scale for video games and gave an example of an adapted ques-
tion, we classified that scale as measuring gaming disorder. Otherwise, we classified the
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measurement according to the original scale from which it was adapted. We also conducted
a sensitivity analysis to examine how our findings differed when other measurements (e.g.,
the Young Internet Addiction Test) were used with a clinical population diagnosed with
gaming disorder. When the clinical population was unclear or was not diagnosed with gam-
ing disorder and Internet addiction scales or other specific measurements/scales/interviews
were used, we did not characterize this as gaming disorder (e.g., Young Internet Addiction
Test in a clinical population of patients with gambling disorder).
• The specific measurement or scale asked questions about specific symptoms of gaming dis-
order rather than only experiences related to video game use in general, such as time spent
playing games or the experience of time loss.
Data on depression and anxiety consisted of study scale, type of analysis, direction of associ-
ation (positive, negative, or null), and how each review reported the outcome of the study (pos-
itive, negative, null, unclear, or absent).
See section above entitled ‘Assessment of reliability of reviews’.
Strategy for data synthesis and reporting
We narratively describe the characteristics of included reviews and their reliability. Because
measurements of exposures and outcomes were heterogeneous, we present counts of positive
or null/negative outcomes from studies and how they were reported in reviews . Because
consistency is one factor that supports strength of evidence, we compared tallies of qualitative
associations from the multiple outcomes reported in studies. We described associations to be
Fig 3. Domains used to define gaming disorder as a construct for analysis. IGD = Internet gaming disorder;
PG = problematic gaming; PIU = problematic Internet use. (a) Sensitivity analysis: Clinical population of those seeking
help for gaming-related problems but an Internet addiction scale was used. (b) Including those adapted from Internet
addiction scales where an example question is given. (c) Where scales referenced appendices or otherpapers, these
were also searched for example questions.
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‘positive and consistent’ at the study level if the count of statistically-significant positive associ-
ations was greater than the total number of negative or null associations. We described an
association as ‘null’ if there were more null findings or negative associations than positive. We
conducted a sensitivity analysis to examine the impact of measuring gaming disorder with a
scale for Internet addiction in a clinical population of individuals with gaming disorder. All
extracted data and derived variables are available in S1 Dataset.
The PRISMA checklist  for the current study is available in S1 PRISMA Checklist. This
study was conducted using publicly-available information and therefore did not require Insti-
tutional Board (IRB) approval.
The searches yielded 842 records, of which, seven reviews were eligible for inclusion in this
overview (Fig 4). The most frequent reasons for excluding articles (at the full-text screening
stage) were that they were not a systematic review or did not specify methods (n = 35), did not
report associations between gaming disorder and anxiety or depression (n = 23), and were not
specific to gaming disorder (e.g., being about behavioral addictions in general) (n = 9).
The characteristics of the seven included reviews are reported in Table 1. They included a total
of 196 unique studies. The number of included studies per review ranged from 24 to 63, with a
mean of 46. Most studies (61.7%) were included in only one review each.
Research question 1: Assessment of review reliability
We found that none of the seven included reviews fulfilled all six criteria for reliability. All
reviews defined eligibility criteria and most reviews (six of seven) conducted comprehensive
database searches (Table 1). No review defined outcomes using all five elements of completely-
specified outcomes (i.e., domain, specific measurement, specific metric, method of aggrega-
tion, and time points). No reviews specified which outcomes of a study would be used in syn-
thesis. One review specified that it would consider only study effect sizes from multivariable
analyses, classifying full associations as “. . .a correlation was found for both genders after mul-
tivariable analyses” or partial associations as “. . .correlation was identified for only one gen-
der” . Other reviews did not specify how outcomes would be included, although some
mentioned that "factors", "disorders", "comorbidity", "health-related outcomes", or "psycho-
social features" "associated with" problematic gaming were "identified" , "ascertained" ,
or "extracted" [30,31].
Although all reviews acknowledged heterogeneity in measurement of problematic gaming,
only one review assessed risk of bias systematically . In this context, because five studies
chose to conduct qualitative syntheses instead of quantitative syntheses (i.e., meta-analyses),
we considered their results to have been combined appropriately. In one review, results were
combined quantitatively despite a very high amount of statistical heterogeneity among studies
(suggested by an I
value of 98%) . Another review classified effect sizes as small, medium,
or large and presented a table of counts of effect sizes for four mental health outcomes as a way
to address heterogeneity in measurement . Most reviews discussed limitations at the study,
outcome, and review level, but two reviews did not discuss limitations systematically [27,29].
Assessment of AMSTAR 2 criteria showed that no study met all criteria, and some criteria
were lacking in all studies. Full results can be found in S1 Data Extraction.
Because of the lack of clarity around how study outcomes were selected, the reporting of
outcomes that was inconsistent with study findings (see Figs 5and 6), the inclusion of studies
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that did not measure gaming disorder, and the lack of systematic assessment of bias (except for
one review ), we determined that review conclusions were not supported by the evidence
from included studies. This is further explored in the following sections.
Research question 2: Distinguishing between gaming disorder and other
Based on our definition for measurement of gaming disorder (Fig 3), no review focused only
on studies that measured gaming disorder. The percentage of studies within a review that mea-
sured gaming disorder ranged from 56.8% to 93.6%. On sensitivity analysis, where measure-
ment of gaming disorder also included using an Internet addiction scale in a gaming disorder
clinical population, the percent remained similar, ranging from 58.6% to 93.6%.
Fig 4. PRISMA flow diagram.
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Table 1. Review characteristics and reliability criteria.
(2) Conducted a
of risk of
51 Unclear Age 0–28 Until 2018 25(56.8) Yes Yes No Yes No No
24 53,889 Any 2011–2017 17 (70.8) Yes Yes No Unclear No No
47 127,749 Any Until 2016 44 (93.6) Yes No No Yes No No
50 129,430 >12.5 years 2005–2016 41 (82.0) Yes Yes Yes No No No
63 58,415 Any 2000–2012 39 (61.9) Yes Yes No Yes No No
58 Unclear Any 2000–2010 33 (56.9) Yes No No Yes No No
30 72,825 Children 2000–2011 20 (66.7) Yes Yes No Yes No No
The number of included studies for a review is taken from the PRISMA flow diagram (where possible) or from reports in the text or tables of each review.
The number of participants was taken directly from the text where possible or calculated from other information that was reported in the review.
If no years were given, the end year was listed as one year prior to the year of publication.
Proportion of studies measuring problematic gaming was assessed out of all studies mentioned in the review. This did not always match the number of studies that were said to be included in the
review in the abstract, methods, or results.
most reviews did not combine results quantitatively.
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Research question 3: Reporting of associations between gaming disorder
and depression or anxiety
Figs 5and 6report the positive and null associations for the depression and anxiety outcomes
according to analysis type (bivariable/multivariable, cross-sectional, and longitudinal), their
frequency of being incorporated into reviews, and how they are represented/reported in
reviews (e.g., not reported, not eligible, report conflicts with outcomes). The shades of blue
highlighting pertain to different percentages of reviews that incorporated a given relevant
result from a given study (darker highlighting indicates higher percentages). Note that only
two negative (inverse) associations were found (between gaming disorder and anxiety) and
because these represent findings that were not positive and significant, they were included in
Fig 5. Associations between problematic gaming and depression. a = Composite reporting of outcomes in review made comparisons difficult.
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the count of null findings. Overall, only the review by Gonza
´lez-Bueso and colleagues 
reported any null results about depression or anxiety from any study.
Associations between gaming disorder and depression. For the depression outcome
(Fig 5, including citations [34–64]), of the 31 studies reporting associations between gaming
disorder and depression, results from 25 were included in at least one review. We found fre-
quent under-incorporation of null results for the depression outcome by the reviews, as sug-
gested by the paucity of blue cell highlights in the null columns. For example, the 2010 study
by Rehbein and colleagues  reported two findings related to depression—a positive associ-
ation between gaming disorder and suicidal thoughts in one subsample, but a null association
between gaming disorder and self-reported depression in the full sample. However, the three
reviews that included this study and reported results for depression all reported them as posi-
Ten of the 31 studies reporting associations between gaming disorder and depression
reported both bivariable and multivariable analyses. In five of these 10 studies, results from
Fig 6. Study reporting of associations between problematic gaming and anxiety. a = Composite reporting of outcomes in review made comparisons difficult.
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both analyses were robust and positive, while five studies reported inconsistent results.
Whether consistent or inconsistent in the studies, positive results were incorporated into five
of the six reviews that included depression findings from the study.
Only one study reporting an association between gaming disorder and depression exam-
ined both cross-sectional and longitudinal associations, and the results were inconsistent .
However, the results were incorporated into two of three reviews as showing a positive associa-
tion. The final review used a composite definition when reporting associations, which made
comparisons difficult .
Six studies reported additional cross-sectional depression results that were not incorporated
into any review. Three of these studies reported null findings and in one of those cases, results
were null in both bivariable and multivariable analyses. An additional 15 studies were men-
tioned by reviews as reporting associations between gaming disorder and depression, but
using domain definitions in Figs 2and 3, these were not found (S1 Output contains full
results). All but one of the six reviews that included these studies reported these as positive
associations. Some reasons for this were: studies used a measure of Internet addiction or other
exposure (e.g., "excessive" gaming), studies reported a composite measure (depression/anxi-
ety/stress) as depression, and possible mistake in citation or data extraction (e.g., reporting
data for a problematic Internet use subgroup rather than problematic gaming subgroup).
In a sensitivity analysis that included studies where a broad Internet addiction scale (rather
than a gaming disorder scale) was used to measure gaming disorder in a clinical population
identified as having gaming disorder, one additional study  was found to have positive
associations and was reported in the single review that included it as positive, while another
three studies [66–68] had null findings which were not reported by the three reviews that
Associations between gaming disorder and anxiety. Of the 28 studies that reported asso-
ciations between anxiety and gaming disorder, results from only 22 of these studies were incor-
porated into reviews (Fig 6, including citations [34–75]).
Six studies reported both bivariable and multivariable associations; half of these showed
inconsistent results. Whether consistent or inconsistent, reviews incorporated only positive
findings. Six studies reported results that were not incorporated into any review; four of these
had inconsistent or null findings. An additional nine studies were mentioned by reviews as
reporting associations between an gaming disorder and anxiety, but using domain definitions
in Fig 3, these were not found. All but one of the three reviews that incorporated these studies
reported these associations as positive.
In the sensitivity analysis, one additional study  reported inconsistent associations in
bivariable and multivariable analysis and was reported as positive in the one review that con-
Research question 4: Association between gaming disorder and depression
or anxiety in reliable reviews
Overall, no review satisfied all the criteria we used to identify reliable reviews, so we could not
address this research question.
This summary of systematic reviews found methodological problems in all seven systematic
reviews that reported on associations between gaming disorder and depression or anxiety;
no reviews could be classified as reliable based on established criteria. Although most system-
atic reviews studied herein defined their criteria for selecting studies and conducted a
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comprehensive search, each review was rated as unreliable because of one or more of the other
criteria. Because of the poor pre-specification of how outcomes would be included, it is diffi-
cult to draw conclusions from these reviews regarding associations between gaming disorder
and depression or anxiety that are supported by evidence. These findings suggest that the way
systematic reviews of gaming disorder have been reporting results and drawing conclusions
may have introduced bias into the gaming disorder literature, possibly misleading future
research, policy-making, and patient care.
Various concerns identified during this summary of systematic reviews are worthy of fur-
ther discussion. We present these in the hope that the current work drives important progress
in research on gaming disorder and other types of behavioral addictions in the coming years.
First, the existing reviews seldom incorporated null findings (i.e., lack of associations) or
negative findings (i.e., inverse associations) from included studies even when the studies
reported such findings. This is a major concern because it seems to represent selective out-
come reporting at the review level. It is vital to conduct systematic reviews and meta-analyses
in ways that are replicable and consistent with best practices to ensure that all evidence is
reported and that relevant studies and findings are not overlooked. Selecting which outcomes
of studies to include in a review without specifying the process, which has been labelled
“cherry-picking” in the clinical epidemiology literature, can lead to biased conclusions at the
review level [10,13]. Completely specifying all elements of outcomes (i.e., domain, specific
measurements, specific metrics, methods of aggregation, and time-points of interest) or explic-
itly noting whether all variations of a given outcome element will be extracted is the current
standard for evidence synthesis [15,26,76]. As incomplete outcome specification may lead to
trillions of potential combinations of meta-analytic results , it is inappropriate to draw
meaningful and reliable conclusions about associations between gaming disorder and the com-
mon mental health problems of depression and anxiety from the reviews summarized in this
paper. Selective reporting of outcomes can be hard to detect, and further research into the
impact of selective inclusion of results in reviews is needed to advance the understanding of
this form of bias on evidence synthesis [77,78].
A second major concern is that reviews did not limit evidence synthesis and conclusions to
studies that measured the construct of gaming disorder and at times used overly-broad defini-
tions of depression and anxiety (e.g., combined depression, anxiety, and stress), which might
have led to reports of associations between gaming disorder and depression or anxiety when
none might exist.
Although more recent reviews had higher proportions of gaming-only measures, even
recent reviews included studies that used Internet addiction questions to measure gaming dis-
order. Distinguishing between problematic behaviors is vital in ongoing research of problem-
atic technology use and will continue to be relevant to shaping the future of health policy and
government regulation of the Internet, video games, and other forms of media and technology.
Ensuring that systematic and accurate measurement of gaming disorder in studies and accu-
rate measurement and reporting of exposures, outcomes, and conclusions in reviews are vital
to inform ongoing decision making regarding diagnosis, treatment, and public health
A third major concern is that only one review  reported a systematic assessment of risk
of bias using multiple domains, which has long been a best practice in conducting systematic
reviews [79–83]. When the risk of bias is not systematically assessed and reported, conclusions
from studies included in reviews may be seen as valid and reliable when they may actually
reflect biases, such as selection bias, information bias, and/or confounding . When evi-
dence of questionable methodologic quality is used to inform public health or policy decisions,
such decisions may be misguided.
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To our knowledge, the current analysis is the first comprehensive examination of selective
outcome reporting in systematic reviews of gaming disorder, a relatively new clinical entity.
Due to this selective outcome reporting, incomplete outcome specification, and lack of system-
atic assessment of risk of bias, we found no reviews that could be considered reliable. These
findings suggest that the evidence base of systematic reviews of associations between gaming
disorder and the most common mental health problems must be improved.
The current overview is subject to certain limitations. First, at the level of the studies we found
significant inconsistencies in measurement and analysis, which were dealt with by describing
counts of associations by type. While this is a somewhat reductionist approach to summarizing
results, it helps paint a picture. Relatedly, no reviews defined outcomes completely. Second, we
limited our analysis to systematic reviews published in English. It is possible that our findings
may have been different had we included reviews in other languages. Third, we focused on the
outcomes of depression or anxiety. This narrow scope made a detailed analysis possible, but
findings regarding associations between gaming disorder and other outcomes (e.g., attention-
deficit hyperactivity disorder) may have been different. However, due to the ubiquitous nature
of selective outcome reporting, in particular, in the reviews herein, we consider this to be
unlikely. Fourth, we defined the constructs of gaming disorder, depression, and anxiety very
specifically; had we used broader definitions, our findings would likely be different. However,
using a narrow definition was our aim. We do not attempt to draw conclusions at the study
level (the 196 studies) due to the inconsistency within studies and the uncertain nature of the
examined evidence. Finally, in our search of PubMed we used the PubMed publication type fil-
ters of “systematic review”, “review,” or “meta-analysis”, while we broadened our search of
PsycInfo to include these terms as text-words in all fields. For this reason, it is possible that we
missed some systematic reviews that were only available in PubMed and were not indexed
using these terms or did not contain these terms in the title, abstract, publication type, or
To advance the field of addictive behaviors and ensure that research measures and reports con-
structs rigorously and with clarity, existing standards for systematic review conduct and
reporting should be followed. Increasing transparency of reviews and minimizing the risk of
bias requires the effort of multiple agents. Authors must prospectively register protocols
(including adequately specifying outcomes); use reporting guidelines, such as those from the
EQUATOR Network; and share data, analysis code, and other study materials. Journals and
editors must verify authors’ adherence to reporting guidelines . Although public health
decision-making should always proceed on the best available evidence , the data provided
in this paper suggest that limiting technology-related diagnoses to video game play is not likely
to accurately reflect the findings of years of research surrounding problematic technology use.
A highly rigorous systematic review that fully specifies outcome domains is needed to clarify
the potential mental health problems associated with problematic technology behaviors,
including video gaming and Internet use.
S1 PRISMA Checklist. PRISMA checklist for reporting of our systematic review.
Evaluating the quality
PLOS ONE | https://doi.org/10.1371/journal.pone.0240032 October 26, 2020 15 / 21
S1 Protocol. PROSPERO registration for our systematic review protocol.
S1 Search Strategy. Search strategies.
S1 Data Extraction. Data extraction at the review level, including AMSTAR 2.
S1 Dataset. Complete analysis dataset containing extracted and derived variables.
S1 Output. Output of analysis.
The authors are grateful to Michael M. Hughes for assistance with the graphic design and for-
matting of figures for publication.
Conceptualization: Michelle Colder Carras.
Data curation: Michelle Colder Carras, Jing Shi, Gregory Hard.
Formal analysis: Michelle Colder Carras.
Investigation: Michelle Colder Carras, Jing Shi, Gregory Hard, Ian J. Saldanha.
Methodology: Michelle Colder Carras, Jing Shi, Gregory Hard, Ian J. Saldanha.
Project administration: Michelle Colder Carras, Jing Shi.
Resources: Michelle Colder Carras, Gregory Hard, Ian J. Saldanha.
Supervision: Michelle Colder Carras, Jing Shi, Ian J. Saldanha.
Validation: Michelle Colder Carras, Jing Shi, Gregory Hard.
Writing – original draft: Michelle Colder Carras, Jing Shi.
Writing – review & editing: Michelle Colder Carras, Jing Shi, Gregory Hard, Ian J. Saldanha.
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