12/09/2025
A New Study Finds For Those Under 12, Cellphones Cause Depression, Obesity, and Sleep Deprivation Issues
When professionals share study results with parents and caregivers in a way that sounds alarming, like the title above, but leaves out the actual context, it’s concerning to us. We should be sharing the best evidence possible with parents and caregivers so that they can make informed decisions. In research, understanding the effect size, often reported as a “Cohen’s d value”, is essential because it helps clarify what the research findings truly mean.
This month, the American Academy of Pediatrics published some new research titled, “Smartphone Ownership, Age of Smartphone Acquisition, and Health Outcomes in Early Adolescence” (1) As a result of this study, some in our field are pointing to it and saying, “aha, here’s the smoking gun that shows for those under the age of 12, smartphones are the cause of depression, obesity and sleep deprivation.” But, is that what the study actually found?
Again, the Cohen’s d in research is a measure of “effect size”, so what did this study actually say?
The study reported odds ratios (ORs) for “associations”: for example, owning a smartphone at age 12 was associated with increased odds of depression (OR ≈ 1.31), obesity (OR ≈ 1.40), and insufficient sleep (OR ≈ 1.62).
When you translate the OR into the actual Cohen’s d value we find the following:
- d = 0.15 (depression)
- d = 0.18 (obesity)
- d = 0.27 (sleep)
In developmental research, effects of d < .20 are commonly dismissed as:
- Noise or background variability
- Artefacts of measurement
- Sociodemographic confounds that weren’t fully controlled
- Statistical effects that don’t translate to real-world outcomes
Even for d ≈ .25, researchers typically interpret the effect as weak, inconsistent, and not policy-relevant unless replicated across many high-quality studies and explained by a clear causal mechanism, which this study does not do.
What This Means for Parents
These effect sizes in this research DO NOT support strong claims such as:
- “Getting a phone before age 12 harms mental health.”
- “Phones cause obesity.”
- “Phones meaningfully disrupt sleep compared to kids without them.”
To say so, and pointing to this study as confirmation, is intellectually being dishonest with parents and caregivers.
What the Cohen’s D value shows us is that in a huge sample of over 10,000 participants , children who got phones earlier, “some” showed slightly different average scores, differences so small they are considered statistical noise, which could be overshadowed by other cofounding facts such as:
- Family dynamics
- Sleep routines
- Physical activity
- Socioeconomic factors
- Personality traits
- School context
- Parenting style
However, we agree that this study does justify continued research that looks more carefully at:
- What kids do with phones
- How parents guide use
- other confounding factors like stress, poverty, loneliness, or family conflict
Again, do we believe that those under the age of 16yrs should have a fully functioning iPhone or Android phone - other than in exigent circumstances, “NO”, and something that we have been preaching about for over two decades! That said, this study isn’t a solid reason to support that view. However, It’s being shared online as it it were by some, and in ways that lack context, which makes it great for attention and engagement, but not for accuracy when it comes to policy or family integration of technology that is developmentally appropriate.
Digital Food For Thought
The White Hatter
Facts Not Fear, Facts Not Emotions, Enlighten Not Frighten, Know Tech Not No Tech
Reference:
1/
10.1542/6383520259112Video AbstractPEDS-VA_2025-0729416383520259112OBJECTIVES. Given concerns regarding health implications of adolescent smartphone use, we tested associations of smartphone ownership and age of smartphone acquisition with depression, obesity, and insufficient sleep in early adolesc...