Welcome to Impact Factor, your weekly screenful of commentary on a breaking medical study. I’m Perry Wilson. And I’m a bad parent.
Yes, that’s what I’ve concluded after reading this study appearing in JAMA Pediatrics.[1]
Screens. They are everywhere. The average US child up to 8 years old spends about 2 hours per day watching a screen of some sort or another, and that number seems to be increasing.
As a good physician, I am concerned about screen use; cross-sectional datahave suggested that kids who spend more time on screens do worse in school and have slower developmental milestones.
But as a bad parent, I am thankful that sometimes after a long day of work, I can put on the TV and have my three kids veg out while I decompress. Here’s a picture of my younger two eating processed food and watching screens while I stand nearby, not enriching their lives in any way.
Up until now, I’ve justified this behavior because prior cross-sectional studies couldn’t assess causality. Sure, maybe screen time hinders brain development, but maybe kids with developmental problems watch more TV, right?
Well, maybe not. The JAMA Pediatrics study gets closer to causality than we’ve ever been before in terms of assessing whether screens can be harmful. Here’s how it worked.
Researchers used data from the All Our Families study, a longitudinal cohort study of mothers and children in Calgary, Canada. There were 2441 children in the study, who were followed from birth to 5 years of age. At yearly visits, mothers were asked about screen usage and were administered the Ages and Stages Questionnaire, a validated survey that assesses child development across multiple dimensions.
Though screen use varied with age, it was pretty high, ranging from 1.6 to 3.6 hours per day. And cross-sectionally, kids who were exposed to more screen time had worse scores on the developmental assessment. Full disclosure: I had to do some back-of-the-envelope math to convert the statistics in the paper to reasonable numbers, but I think this is pretty close:
That finding doesn’t add much to the existing data. But the researchers went further. They used a technique called random-intercept crossed-lagged panel modeling to tease out the direction of causality between screen time and development.
Source: Madigan S, et al[1]
It’s complicated. But basically, since the kids were followed over time, the researchers could ask two questions:
- Did screen exposure at a younger age associate with slower development later?
- Did slower development at a younger age lead to more screen time later?
The answer to number 1: Yes; number 2: No.
For each extra hour of screen time per day at 24 months, for example, developmental scores at 36 months were 0.3 points lower (on a 60-point scale), a statistically significant difference, whereas there was no relationship between developmental scores at 24 months and screen use at 36 months.
This is fairly compelling evidence that the direction of causality is pointed pretty squarely from screen time to slower development.
But bad parents like me should not fear that their precious 30 minutes of quiet time after dinner need to be thrown away recklessly. Here are some of the caveats.
First, the overall effect here is really small. Even 20 extra hours of TV a week would decrease development scores by only about a point, which may not be clinically significant.
Second, there was no breakdown of the type of screen time, which can be interactive and social or totally passive. It can be mindless or surprisingly informative (I’m looking at you, Magic School Bus).
Finally, there was an almost equally strong association between maternal depression and developmental scores, which supports an argument that I’ve made a lot when it comes to childrearing: that parental sanity is important for child development, and if taking a break from your kids for a bit helps with that, well, it may just be worth it.
Nevertheless, as a physician, I feel the need to say that we should all encourage our patients to spend time with their kids, play with them, and help their little minds develop the ability to interact with real-life people.
And if you’re a bad parent like me, remember—it’s never too early to start building critical card-counting skills.
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