Does Excessive Screen Time Cause ADHD?

Debate continues to rage regarding the possible harms of too much screen time, especially for children. Recent media reports have suggested a link between the amount of screen time that children experience and attention deficit hyperactivity disorder (ADHD).^1,2

Clearly, this suggestion is of considerable concern to all, especially to parents, but such views are not without their critics. Some health regulators take a cautious approach to such suggestions,³ and some media companies, like the BBC, who are committed to developing digital platforms, articulate a wary view.⁴ The contradictory reports and views create confusion and worry among parents, so it is important to look at the evidence; exploring whether there are any clear answers, and, just as importantly, what are the questions that need to be asked?

Focus on whether exposure to screen time causes one particular problem, or another, certainly makes a good headline and gets people talking about the issue, but this may actually be directing the debate into misleading areas or an intellectual cul-de-sac. Analysis of what can, and cannot, be concluded from any one study may illustrate these problems, and highlight alternative and more pertinent questions to be asked, before furthering the debate and attempting to isolate the themes and important issues in the literature.

One recent study prompted considerable media discussion over links between screen time and the development of ADHD.⁵ In this study, an average of about one-and-a-half hours a day of screen time was found across a large sample of three- to five-year-old children. Once screen time exceeded two hours a day, there were "clinically significant" higher levels of externalising behaviours and attentional problems—behaviours highly similar to those noted with ADHD. The link between screen time and these symptoms was stronger than for any other measured factor, including that of parenting stress, which I and my colleagues have found to be an important predictor of child behaviour problems.⁶

Before critiquing the interpretation placed on this study in the media, it needs to be pointed out that this was a good study. It raises concerns and questions about the psychological safety of too much screen time, but it did not claim that screen time causes ADHD. As widely reported concerns emerged about the implications of this study’s findings, it is worth exploring what was really important about the study, and what could be misdirecting coverage.

The study demonstrated an association between screen time and some behaviours associated with ADHD. Now, a collection of behaviours associated with ADHD is not the same thing as ADHD itself, which is important to remember. A condition is defined by the more or less constant conjunction of a set of symptoms, not one or two symptoms that may occur in isolation from one another. To say that individual behaviours connected with ADHD are ADHD misses the point; these behaviours may form part of their own cluster associated with screen time problems, and to look at them in the context of ADHD may misdirect that debate. A screen time problem may look a bit like ADHD, but it may be, in fact, its own problem—a novel problem for the digital generation.

We also need to be clear that the study did not show a causal link between screen time and problem behaviours, ADHD-related or not—meaning that we cannot conclude that excessive screen time causes ADHD (or anything else) from these data alone. However, we do need to be sensible and acknowledge that some things just cannot be established by experimental means. We cannot manipulate screen time to see if it might produce ADHD: one, it is unethical; and, two, it is too difficult. That said, it has been shown experimentally that reducing screen time does reduce depression,⁷ so this criticism loses some of its weight when taken in the round of scientific possibilities.

Another view of these data is that those with ADHD use screens more often—or it may be that the relationship goes both ways.⁸ Of course, we can place any interpretation on such correlational data to suit our own biases, but we have to consider which interpretations are more likely. Alternatively, we could suggest that some other factor leads to both ADHD and the increased use of screens. So, what would be a third factor controlling both screen time and mental health problems? "The spirit of the age" has been suggested⁹—but this is adding an ill-defined concept into an undefined relationship, and is hardly helpful in moving the debate forward.

A more practical and definable problem to consider, in relation to this study,⁵ is the meaning of "screen time." The study used a parental-report measure of this variable, but are such subjective measures reliable, or are they the most important measures to take? Is screen time a proxy-measure for some other more important variable, like digital dependency?

Also, the study added together all screen time experienced by the participating children—TV, computers, social media, etc. However, it is not clear that these different forms of screen time have the same effects as one another. Some unpacking is needed here. It may be that TV is still "social," in a way that social media is not—and this may make a difference to its outcomes.

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Having got the interpretative problems relating to this study out of the way, it is very important to note that picking away at one study will not destroy the whole evidence-base, and considering the totality of the evidence is critical. No single study can answer such big questions, and the above study has helpfully prompted an important debate. Beyond this study, are there other reasons to believe that screen time is associated with (or even causes) behavioural and cognitive problems?

In fact, there are plenty of studies showing a link between "personal" screen time (that not associated with work) and worse mental and physical health—particularly concerning impacts on attention and impulsivity,¹⁰ including some experimental demonstrations from my own lab.¹¹ A further wrinkle to consider is that these studies suggest that it may not be screen time, per se, that is key, but rather the damaging psychological effects screen time may have for an individual, which are then associated with behavioural problems—that is, screen time is a proxy-measure for digital dependency.

Nevertheless, these sorts of data back up the conclusions that screen time can be related to symptoms reminiscent of ADHD (but not necessarily meaning ADHD), like attentional problems and impulsivity. This view is reinforced by findings showing that changes to the frontal cortex are associated with excessive screen time—a brain area implicated in such cognitive and behavioural control issues.¹²

It is important to highlight that these associations might not apply to work-related screen time, although whether this category also includes uses for educational purposes, that might impact children, is completely unclear. Certainly, the OECD suggested that increased levels of ICT in the classroom correlates with increased behavioural problems.¹³

If we are to accept the horror of a link between screen time and such behavioural problems—and think, for a moment, of the implications of the putative fact that the single biggest development of the twenty-first century may be damaging children in profound and possibly irreversible manners—then what causes this damage Is it a matter of neurological damage,¹² perhaps mediated through hormonal factors or triggered by digital-withdrawal stress? Alternatively, are there learned effects of exposure to screens that produce these behavioural and cognitive changes?

The study in question⁵ suggests a possible "socialisation" solution to the problem. A protective factor against the negative impacts of screen time was found to be structured activity—not any old activity, but two hours a week of organised games/sport in a social context.⁵ Perhaps it is the lack of structure or routine, resulting from too much solo screen time, which causes the ADHD-like behaviours seen for children using screens for long periods?

A similar explanation may underlie the effects of initiatives like breakfast clubs—premised on speculation about what various nutrients do to cognition, it may be that they just socialise children better! Certainly, this is the premise of the Daily Living Skills schools for children with ASD. It could be the same for behavioural and cognitive problems associated with digital screens.

It is also worth considering that exposure to immediate, as opposed to delayed, outcomes has been shown to cause (note the word "cause"—because this is experimental evidence) subsequent impulsivity in rats.¹⁴ Exposure to immediate outcomes in phase one was found to produce greater impulsivity in phase 2 than previous exposure to delayed outcomes. A feature of some screen time is this immediacy of outcome—potentially provoking an inability to tolerate delays.

This brief meditation on the possible harms of screen time, and their causes, throws into sharper contrast the real possibilities of a cigarette-like inducer of harms for the young. This does not mean that screen time causes ADHD, but it may well be causing something else—a new problem that we have not seen before. The evidence is growing, and ignoring this problem, or disputing the results of a single study, will not make it go away.