A few weeks ago, we saw a surge of articles saying that excess screen time can cause early puberty in kids. hat's a pretty frightening prospect, and the claim naturally received a lot of press attention. The study that prompted all of the articles, however, doesn't show any such thing.
First, it was a study of rats, and only 18 of them. It is true that rats have similar development to humans and studies provide helpful information. However, as one of the study's authors said, very far down in the press release in an easily overlooked section, we can't draw exact parallels. Similarly, the study looked at only 18 subjects, meaning that we need to see replication in larger samples before we start drawing conclusions. Furthermore, the paper was presented at a conference, which has a lower threshold of validity than peer-reviewed journals.
Finally, the test conditions didn't accurately replicate actual human screen times. The study apparently exposed the rats to ONLY blue light for part of their day. Humans rarely have only blue light for long periods of time. It's also quite possible that the test conditions caused stress for the rats because it interfered with their usual sleep cycles. In fact, the only hard finding is that the rats exposed to more blue light showed lowered melatonin levels. Although the researchers were monitoring other chemical levels, including those related to puberty, there were no measurable changes in the rats exposed to blue light.
The hype around this study illustrates the importance of follow-up studies and replication. Until we see more studies replication these results, we shouldn't be citing this study. There are many good reasons to be concerned about how much time children spend with electronics. This study is not one of those good reasons.
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