Now that we are on the other side of the pandemic, we are starting to see the toll it has taken on our youth. Mental health problems have soared, obesity rates have increased, and the newest post-pandemic phenomena is pre-adolescent girls experiencing an abnormally early onset of puberty, also known as precocious puberty. Many studies have noted this trend across the globe.1

Unlike mental health problems and obesity, which are clearly linked to children spending unnatural amounts of time being inactive, indoors, and lacking socialization, the link between early puberty and the COVID-19 pandemic isn’t as clear. There is no evidence to suggest that COVID-19 infection itself affects hormone levels or puberty timing. Some experts attribute it to the rise in obesity rates that we’ve observed over the pandemic, as it’s well established that girls with increased body fat tend to mature earlier.

The latest hypothesis is that an increase in screen time and subsequent blue light exposure is to blame for early puberty onset. Tablets and smartphones emit this blue light, or high-energy visible light. Previously, blue light exposure during evening hours has been linked to a variety of health problems, including the disruption of one’s circadian rhythm, which is vital for good sleep. Studies also show that a dysregulated circadian rhythm may play a role in many mental health issues.2 Other preliminary studies speculate that blue light exposure during evening hours may increase insulin resistance (the ability of the body to take up glucose from the blood) and influence metabolism.3

The link between blue light exposure and the early onset of puberty was studied by researchers from Gazi University and Ankara City Hospital in Turkey and recently presented at the 60th Annual European Society for Pediatric Endocrinology meeting on September 16.4 As part of the study, they exposed female rats to a spectrum of light predominantly emitted by LED screens for relatively short or long periods each day. They found that the rats that were exposed to blue-tinged light for longer periods of time showed earlier puberty onset, reduced levels of melatonin, increased levels of some reproductive hormones, and physical changes in their ovaries.

It is unclear whether blue light filters or blue light-blocking glasses that are known to be effective at preventing eye strain are also protective against dysregulation of the circadian rhythm and the potential metabolic effects of blue light, and, by extrapolation, precocious puberty. Most experts agree that there isn’t enough conclusive data to make that connection yet, but there are some smaller studies that look promising.

Many experts are rightly hesitant to make the firm conclusion that the above rat findings can be extrapolated to humans, including the author himself who cautions, “as this is 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.”

The data so far isn’t quite persuasive. More studies need to be done to understand the effects of blue light on children and ways to protect them from the potential harmful effects, but even if this rat study does end up having any truth to it, it is likely one factor, amongst many – including increased obesity rates and environmental factors – that is causing an increase in early puberty onset.

In any case, it’s always important to be thoughtful about the amount and type of screen time that our children are exposed to – for the reasons above, but more importantly, for the many known negative effects that screens can have on our youth. In our modern world where screens are so heavily relied on, this may sound like a challenging feat. Establishing media priorities in line with your families values, setting a family media plan that sets boundaries around screen time usage and an overall increased thoughtfulness around the use of screens in the home may be a good place to start.