No, a study did not find screen time causes early onset puberty

No, a study did not find screen time causes early onset puberty
How did a small, unpublished animal study become international news purporting to be evidence smartphone screen time causes early onset puberty?
How did a small, unpublished animal study become international news purporting to be evidence smartphone screen time causes early onset puberty?
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How did a small, unpublished animal study become international news purporting to be evidence smartphone screen time causes early onset puberty?
How did a small, unpublished animal study become international news purporting to be evidence smartphone screen time causes early onset puberty?

Scientists have criticized new research claiming excessive smartphone use can be linked to early puberty onset. The research is unpublished, yet to be peer-reviewed, and was promoted through a press release packed with wild speculation, offering a perfect case study in bad science communication.

On Friday September 16th, a number of news headlines popped up, reporting on some pretty startling new research. Apparently scientists had discovered “Excessive Smartphone Use Could Bring On Early Puberty In Children.” According to the news, exposure to blue light, via smartphone or tablet screen time, could alter a child’s hormone levels and hasten the onset of puberty.

But is this really what the research found? And how did this speculative story suddenly spread so widely?

The story begins with some new research findings presented last week in Italy at the 60th Annual European Society for Paediatric Endocrinology Meeting. The findings, from a team of scientists at the Gazi University Faculty of Medicine in Turkey, reported on a study that exposed immature female rats to extreme durations of blue light.

According to the conference abstract, the only data available from the unpublished research, six control group rats (treated to standard 12 hour light / 12 hour dark lab conditions) entered puberty on the 38th day of the experiment, while the six rats exposed to an additional six hours of blue light every day entered puberty on the 32nd day of the experiment and the 12-hour blue light exposed group hit puberty on day 30.

A number of metabolic markers were also tracked in the rats, but they were all the same regardless of any blue light exposure. The only hormonal marker the researchers could report linked to blue light exposure was a reduction in melatonin levels.

That’s it. That’s the research. As the University of Cambridge’s Amy Orben explained, this kind of blue light exposure is in no way analogous to exposure from smartphone or tablet screens. So any translation to humans falls apart right here.

“This study done on rats give us little to no evidence about what would be found in human children,” Orben said. “Further, pure blue light exposure for long durations is not an accurate portrayal of young people’s screen use. This is especially the case for the 12 hours of blue light condition in the study, which would have made a very stressful environment for the rats.”

Kevin McConway, a statistician from Open University, echoes Orben’s concerns, pointing out the huge leap from what the research found and any conclusion about how smartphone screen time could affect puberty onset in human girls.

“The rats were exposed to blue light, seemingly to the exclusion of any other light, for either half or all of the light time of each of their days,” McConway said. “Also it may be relevant that wild rats are mainly nocturnal, and despite the behavior of some young humans I’ve met, humans do tend to be rather less nocturnal, so that responses to light of any kind in rats and in humans may not necessarily match.”

So how did this small study in 18 rats suddenly become a story about smartphones and puberty in children?

Accompanying the conference presentation came a press release from the European Society for Paediatric Endocrinology titled, “Excessive smartphone screen time linked to earlier puberty onset."

This press release does all the heavy lifting not in the actual research, starting with the flat-out incorrect headline before linking blue light exposure to smartphone use, and then presenting the unproven hypothesis that smartphone use at night inhibits sleep by disrupting melatonin release. Finally, the press release draws a connection between melatonin and puberty onset, ultimately allowing for the ultimate speculation:

“In recent years, several studies have reported increases in early puberty onset for girls, particularly during the COVID-19 pandemic,” the press release from the European Society for Paediatric Endocrinology stated. “The link between blue light exposure and reduced melatonin levels suggests that increased screen time, such as during the pandemic restrictions, may be playing a role in this reported increase.”

A direct quote from one of the researchers involved in the study does caution the findings are only in rat models. So there is no direct presumption from the researchers that their findings conclude blue light exposure hastens puberty in human children. But, the researchers also seem very clear about what their findings are gesturing towards, ultimately recommending parents of young children should be careful about exposing their kids to blue light.

“As this a rat study, we can’t be sure that these findings would be replicated in children but these data suggest that blue light exposure could be considered as a risk factor for earlier puberty onset,” said Aylin Kilinç Uğurlu, one of the researchers working on the project. “Although not conclusive, we would advise that the use of blue light emitting devices should be minimized in pre-pubertal children, especially in the evening when exposure may have the most hormone-altering effects.”

Pete Etchells, a professor of science and science communication at Bath Spa University, said this kind of research should be very carefully covered in the media, if covered at all.

“Unpublished and unreviewed research should be heavily caveated in the media, if it is going to be covered at all,” said Etchells. “Unfortunately, the press release here does not do a particularly good job of representing the underlying science.”

This saga is a perfect example of the problems and perils in modern science communication. The dirty little secret in science journalism today is that, much like most areas of journalism, it's driven by press releases. And when those press releases dramatically stretch research findings beyond the basic science it is easy for some journalists to succumb to hyperbole and misunderstandings.

There is nothing inherently unusual, or improper, in reporting unpublished findings announced in the context of a scientific conference. What is unusual here is that such a small, unremarkable study has been amplified and misrepresented to such a large degree.

“I am surprised this is raised, as an unpublished abstract from a small conference, rather than once it is a published paper,” noted Stuart Pierson, an expert in circadian neuroscience from the University of Oxford. “Without attending the meeting or seeing the data I cannot accurately judge the science, but from the available information in the abstract, it would be overclaiming to say these findings have any significant relevance to humans, their screen use and puberty.”

While journalists who uncritically regurgitate inaccurate statements from press releases are certainly part of the problem, so are the communicators who write the original media releases and the scientists who explicitly deliver the speculative soundbites knowingly designed to misrepresent their core findings.

Here, a truly extraordinary press release from the European Society for Paediatric Endocrinology has framed a small animal study into a discovery that feeds into the popular, yet unproven, notion that smartphone or tablet screen time is damaging our children. And regardless of how balanced an outlet’s article on this research ends up, the headlines that frantically circulate social media have already done their job.

DJ's "Feed Me Doggie"
As we used to say about K-Mart, you get your money's worth. Especially during the 'Blue-Light Specials".
Nice article Rich. But you didn't toy with the hypothesis - if you sleep less, you get horny faster. We knew that in High School - those who could stay up late and slept less seemed to "get lucky" more often. Don't know how long some of those guys and gals have lived, but in their teens, they sure pretended to be more mature, don't you know.
I don't know how much it had to do with blue light - but I can see how it can be effected by melatonin levels.