Letters Response

Susan Greenfield replies to Vaughan Bell and colleagues

BMJ 2015; 351 doi: https://doi.org/10.1136/bmj.h4960 (Published 17 September 2015) Cite this as: BMJ 2015;351:h4960
  1. Susan Greenfield, senior research fellow, Lincoln College Oxford, and CEO, Neuro-Bio1
  1. 1Lincoln College, Oxford OX1 3DR, UK
  1. susan.greenfield{at}pharm.ox.ac.uk

A year after I wrote Mind Change, Vaughan Bell and colleagues claim I’m scaremongering about potentially adverse effects of internet and computer use.1 They assert there’s no evidence that “typical internet use harms the adolescent brain.” Tellingly, they don’t define “typical use” or reflect on the escalating use preoccupying children—crucial omissions given reports from Ofcom,2 3 the House of Commons Health Committee,4 and Public Health England.5

Recent research shows teens using screens for an average of 10.75 aggregated hours daily.6 Such findings raise the all important question: where should we draw the boundaries between harmless use and misuse? Change in brain structure and function in response to experience is a well-established phenomenon. High levels of multi-tasking,7 internet use,8 or playing video games9 are associated with significant differences in the anterior cingulate cortex,7 8 dorsolateral prefrontal cortex,8 supplementary motor area,8 orbitofrontal cortex,8 cerebellum8 and/or ventral striatum9. With internet addiction, the reductions in certain prefrontal functions and striatal dopamine receptors and transporters resemble those in other addictive disorders.10 11 12 13 As discussed throughout Mind Change, the chicken and egg problem applies to many such findings. Nevertheless, evidence indicates that duration of internet addiction is negatively correlated with grey matter volume at various cortical sites8 and that attention problems are both a consequence of and a predisposing factor for protracted video gaming,14 an activity associated with acute striatal dopamine release.15

Although Bell and colleagues claim that social networking “enhances” friendships, increased use of social media does not correlate with a larger offline network or feeling closer to friends in the real world.16 The editorial overlooks peer reviewed studies reporting adverse effects of social networking such as increased volatility and narcissism and reduced self esteem, along with distortions of the sense of self.17 18 19 20 21 22 23 24 25 26 Although they assert “people generally portray their identity accurately,” various studies refute this.27 28

Bell and colleagues insist it’s “entirely implausible” that screen technologies influence the development of autistic-like traits. Dr Leonard Oestreicher’s rapid response on thebmj.com challenges this29; furthermore, links between those traits and screen technologies have been reported.30 31 32 33 34 Regarding video games, they state “multiplayer cooperative games are increasingly common, and evidence suggests these kinds of games might lead to an increase in socially beneficial thoughts and behavior.” But the dominant narrative in popular games concerns men engaged in violence.35 Repeated exposure to media violence diminishes responsiveness in an inhibitory frontolimbic network36; a recent meta-analysis concluded that violent video games increase aggression.37 Bell and colleagues acknowledge “valid concerns . . . about digital technology”; with video games they focus on “displacement” of academic activities, a concern that’s beyond dispute.38 But it’s not clear why they overlook concomitant displacement of real world interactions and thereby opportunities to develop socially beneficial thoughts and behaviour.

Bell and colleagues take exception to my reasoning that reliance on search engines may foster superficial mental processing at the expense of deep knowledge and understanding, but concede “when people know they can access information . . . they are less likely to remember the content.” They note this effect “is not restricted to the use of technology . . . people who work in teams are less likely to remember facts when others hold the information.” Thus, memory is vulnerable to factors including screen technologies.

A further criticism is that I haven’t submitted my arguments to peer review. But Mind Change is a book presenting the results of numerous peer reviewed studies in neuroscience, psychology, sociology, and epidemiology. Furthermore, publications since Mind Change indicate that it’s an increasingly validated wake-up-call.6 7 10 13 34 37 39

Given that the digital world offers unprecedented multifaceted possibilities, we should be alert to its opportunities and threats. Bell and colleagues conclude: “the public deserves to participate in the debate fully informed of all the evidence.” That’s why I wrote Mind Change.


Cite this as: BMJ 2015;351:h4960



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