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expert reaction to scoping review paper looking at screen time, green time and psychological wellbeing in children and adolescents

Research, published in PLOS ONE, looked at relationships between screen time, green time and psychological wellbeing in children and adolescents.


Dr Bernadka Dubicka, Chairwoman of the Child and Adolescent faculty at the Royal College or Psychiatrists: 

“The potential benefits or harms of screen time are highly complex.  They depend on a wide range of factors including the type of screen use, pre-existing mental health problems and social factors such as deprivation.  Although this extensive review attempts to separate out studies looking at different age groups, socio-economic status, as well as longitudinal studies, it’s not able to address this level of complexity.  The review is also limited by its nature – it is a scoping review with no attempt to examine the quality of the research or quantify effects, and evidence is still emerging. 

“Research into the effects of green space is even more limited, and more studies are needed.  While we wait for further evidence, it is important, especially during this pandemic, that we support children and young people to have a balance of activities in their lives.  This means access to green spaces and the mental health gains that come with it but also using screens safely to minimise potential harms.” 


Prof Dame Til Wykes, Vice Dean Psychology and Systems Sciences, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, said: 

“The systematic review was thorough but the majority of papers (62%) were cross sectional and only 19% of the reports followed people up over time, making it very difficult to detect causal relationships between screen or green time and psychological difficulties.  As the authors say, we need robust science with longitudinal high quality studies and the authors didn’t assess quality. 

“A study from NIHR (Widnall et al, Aug 20201) investigated longitudinally the relationship of screen time and mental health and discovered little evidence for negative consequences despite the increase in the use of social media by girls during the pandemic.  The increased use may have been one of the ways that supported connectedness and wellbeing.  Screen time effects depend on what type of screen you are talking about. 

“Screen time is much more complex than measuring the hours online, even more so when it is your parents who are counting.  The review should not be read as meaning parents need to take more control and cut down media use.  It all depends on what children do with their time and a mix of activities is what most children need.  It may also be a lifeline for adolescents who need some social support even if a distraction from family time.” 



Dr Sam Wass, Senior Lecturer in the Department of Psychology, University of East London, said: 

“This review documents the associations that have been shown between the amount of time people spend looking at screens, and interacting with nature, and various psychological outcomes including mental health, cognitive functioning and academic achievement.  Although these associations are strong, and have been shown across a number of different studies, it’s important to be clear that almost all of the studies are correlational.  The problem is that families who live closer to green areas differ in lots of ways from those who live in urban settings – and it’s impossible to be sure that it’s the greenery itself that’s causing the difference.  Similarly, families where the children get more screen time differ in lots of different ways from families where the children get less – and it’s impossible to be sure that it’s not one of these other factors that are actually affecting psychological outcomes.  This is a very tricky question for scientists to answer. 

“Another question that the authors could have examined more is the question of why green time might be affecting psychological outcomes.  For example, it could be that simply having lots of space to run around is what’s really important.  But other studies suggest that simply putting up pictures of trees and greenery can affect psychological outcomes – even if the space itself doesn’t change at all.  Answering these types of questions is essential for maximising the usefulness of this research for families who don’t naturally have access to green spaces. 

“Similarly, for screen time, it’s important to consider how people are using screens.  There are important differences emerging between ‘passive’ screen use (such as watching TV) and ‘interactive’ screen use (using as playing computer games, or social media) – but this review doesn’t really consider those.  Many psychologists would agree, though, that there’s no point trying to ‘wish screens away’.  The most important task is to maximise the potential benefits that we can get from interacting with screens, while minimising any potential harmful effects.” 


Prof Kevin McConway, Emeritus Professor of Applied Statistics, The Open University, said: 

“This research must have been time-consuming and demanding to carry out, and it could well be useful to other researchers.  But it can’t tell us anything at all clear or definitive about how screen time or green time might be associated with psychological outcomes in children and young people.  Indeed that isn’t even its stated intention in any way – it’s important to understand that.  Really the only fair short summary of the position it finds is: “It’s complicated”. 

“This is a scoping review.  Scoping reviews have been described as a technique for mapping the existing research, usually in a broad area and not concentrating on just one or two precise issues.  A scoping review does not normally assess in detail the quality of the studies that it reviews, or look at how likely it is that their results are biased.  And though there will often be general comments on the research findings, the aim is not to produce a definitive conclusion on where the research is pointing.  A scoping review does not include a meta-analysis, the statistical approach to summarising the findings from several related pieces of research.  So a scoping review, like this one, does not even aim to answer specific questions like “Do children who watch screens a lot differ, in psychological terms, from children who watch screens less?”  That’s not the point – the point is to map what has been researched before and to make clearer for future researchers what has already been done and where the gaps are.  So the comments that the researchers make about possible associations between screen time, green time, and psychological well-being are not based on a full, detailed, statistically solid evaluation of previous research, simply because that’s not the point of this work.  It’s a bit of a cliché that so many research studies end up concluding that more research is needed – this review does that too, but its aim is to throw light on where future research can help most. 

“The fact that this research considers, in the same report, both screen time and green time might lead one to think that there has been a lot or previous work looking at these things together.  In fact the scoping review shows that that is not the case at all.  The researchers base their findings on 186 previous studies.  Of these, most (114 of them) were about screen time alone, quite a few (58) were about green time alone, and just 14 had elements of both.  To get that number up to 14, the researchers had to include studies that did not meet one of their general overall criteria for being included at all.  (They included screen time studies only if the studies measured the time spent on two or more different screen-based activities – unless they looked at green time too, in which case they could be included with just one screen-based activity.)  The majority of the 14 studies that considered both screen time and green time would not have got into the review if it had not been for the weakening of this criterion.  It’s also clear from the descriptions in this new research that a lot of the 14 studies were actually interested mainly in either screen time or green time, and included some measurements of the other one only to make statistical adjustments to their findings.  So the most obvious conclusion on previous research looking at screen time and green time together can only be, “There’s hardly any of it.” 

“So if screen time and green time haven’t often been researched together, why are they looked at together in this new research?  An oversimplified summary of the researchers’ reasons seems to be that, over the years, the time young people spend looking at screens has increased while the time spent outdoors has reduced (though other changes in time use have occurred too), and that there has been concern that too much screen time might not be good, and that lots of green time might be good and perhaps even reduce any harmful effects of screen time (though there’s next to no data on that).  But several previous reviews have not found an overall message that screen time is bad – the position is complicated and it does depend very much on exactly what the young people are looking at on their screens.  And anyway, the possibility that screen time and green time may work in opposite directions is not on its own a reason to look only at screen time and green time together, at least not without looking at other ways young people spend their time as well.  If screen time is bad for young people – and as I’ve said the evidence for that is not at all clear, overall – then why choose only green time as a possible alternative, and not other activities that have often been regarded as good in psychological terms, such as playing sport or performing music or spending time with one’s family? 

“One aspect of the studies that are reviewed in this new research is that the findings may often be partly determined by what the researchers on the original studies decided to look for.  The new study characterises the previous studies according to the type of psychological outcome they investigated.  Overall, more studies looked at indicators of poor mental health than at indicators of positive mental health, but there is a difference between screen-time and green-time studies.  On green-time studies, the number looking at positive mental health outcomes was almost as large as the number looking at poor outcomes, but on screen-time studies, the difference between these numbers was larger.  This imbalance between the two is not huge, but it may indicate that screen-time researchers are coming to their research with the initial view that screen time is bad for young people, under some circumstances anyway, and perhaps green-time researchers are doing this less often.  If a piece of research looks only at potential bad outcomes, then it’s not going to be able to find positive evidence of good outcomes – the best that could happen is that it fails to find evidence for the bad outcomes, which is much weaker. 

“The choice of outcomes to research is one question that was examined in important study on electronic media use that was published last year1.  This analysed the same (large) sets of data in thousands of different ways, any one of which might have been chosen by researchers.  These different approaches varied in the measure of well-being that was used, the measures of media use, and in several other ways.  They found that different choices could lead to very different findings of associations from the same datasets, ranging from quite strong negative to quite strong positive associations between media use and the well-being of adolescents.  So how you choose to look at these issues can strongly affect what you find.  (You might wonder why this study was not included in those reviewed in the scoping review.  I wondered that too – it was published in January 2019, just before the cut-off date of 18 February for inclusion in the scoping review, but perhaps it had not yet made its way into the databases that researchers used for the main searches.) 

“Another contrast between the screen-time and green-time studies that perhaps casts light on the orientations of the researchers in those studies is their choice of research methods.  For screen time, all 114 studies that are in the scoping review used observational methods.  In observational research, there are substantial problems in showing what causes what.  Children who spend a lot of time using screens will differ in many ways from those who spend less time, and these other ways may be the real cause of any differences in psychological outcomes.  Indeed, three-quarters of the screen time studies were cross-sectional, which means that they recorded screen time use and psychological factors at the same point in time.  In a cross-sectional study, you can’t even clearly rule out the possibility of reverse causation, that is, that the psychological factor causes the differences in media use, rather than the other way round.  The other quarter of these studies used longitudinal or cohort methods, which at least generally rule out reverse causation but can leave other questions of cause and effect largely unanswered.  The green-time studies were also mostly observational, of different kinds, though fewer of them were cross-section (38%), several incorporated aspects of experimental design, and a few were even randomised controlled trials, where the position on what causes what can be considerably clearer.  Maybe the much greater use of cross-sectional observational studies in screen time work, in contrast to green time work, is related to a prior view from screen time researchers that screen time is bad for children, while green time researchers are less likely to feel that green time is bad for children.  Here I’m speculating really, but I do have a concern that researchers may not always be neutral enough, and may (consciously or unconsciously) choose research approaches that fit what they think they should find.  The scoping review specifically looked at the extent to which previous research could throw light on causal links, but, rightly since this is a scoping review, it generally describes what was done rather than drawing clear specific conclusions.  It also specifically looked at the question of whether associations between screen time, green time and psychological effects might differ depending on the socio-economic status of the families involved.  I think this is an important question.  The position there seems again to be complicated, and, rightly again, the researchers in the scoping review mainly describe what was done in the studies that they review rather than drawing overall conclusions. 

“One concern that I have about the scoping review is whether, in fact, the researchers managed to find enough of the relevant pieces of previous research that they sought to review.  The research is described as a systematic scoping review, and the word ‘systematic’ is used because the researchers sought to find all the relevant previous work.  They used the usual methods of searching standard research databases, and first screening the resulting lists to find which research papers were really relevant.  That process gave them 114 papers to review.  They then carried out an important further step of looking in the reference lists of those papers to see if they listed other work that the previous searches had missed.  Some new work does generally turn up in this step, but in this case there was a great deal of it (another 60 papers).  This seems to have been because researchers use very varied terms to describe what they are doing in research on these matters, and so a lot of relevant work had been missed by the original database searches.  However, work that did not use the terms in the database searches, and that also was not referred to in reports that did turn up in those searches, would very likely have been missed entirely, and there’s no way of telling how much of it there is.  Indeed the researchers themselves point out that failure to find all the relevant previous research may be a limitation.  Another key limitation, that the researchers are right to mention, is that they considered only the time spent using screens, not what specific content the young people were looking at.” 

1 Orben and Pryzbylski (2019) ‘The association between adolescent well-being and digital technology use’, Nature Human Behaviour, 



‘Psychological impacts of “screen time” and “green time” for children and adolescents: A systematic scoping review’ by Tassia K. Oswald et al. was published in PLOS ONE at 19:00 UK time on Friday 4 September 2020. 

DOI: 10.1371/journal.pone.0237725 


Declared interests 

Prof Dame Til Wykes: “I don’t have any conflicts.” 

Dr Sam Wass: “I have worked as a media spokesperson for companies including Lego, Fisher Price, Aardman Animations and Nikleodeon.” 

Prof Kevin McConway: “I am a member of the SMC Advisory Committee, but my quote above is in my capacity as a professional statistician.” 

None others received. 


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