“One possible explanation for these results is that parents are doing a good job of tailoring their decisions to give their children their phones to the needs of the child and their family,” Robinson said. “These results should be seen as empowering parents to do what they feel is right for their family.”
Buying the phone early wasn’t associated with problems, he noted, but neither was buying the phone late, and “if parents want to delay, we didn’t see negative effects from that either.”
Assessment of children’s well-being
When deciding to give a child a cell phone, parents usually weigh many factors, such as: if the child needs a phone to let parents know their location, access the Internet, or maintain social connections; how much the phone can distract the child from sleep, homework or other activities; and whether the child is mature enough to handle risks such as exposure to social media, cyberbullying or violent online content.
Previous research into the effects of children’s cell phone ownership has had mixed results, with some studies suggesting phones impair sleep or grades and others showing no effect. Previous studies were limited because most of them collected data at only one or two time points.
In the Stanford Medicine study, the children were 7 to 11 years old when the study began and 11 to 15 by the end of the research. Each child and one of their parents participated in assessments at baseline and annually thereafter, for a total of five assessments per participant.
At each assessment, parents were asked if their child owned a cell phone and if it was a smartphone. The time interval between the last visit when the child did not own a phone and the first visit when he or she owned a phone was calculated as the age of purchase.
At each visit, children completed a standardized questionnaire to assess depressive symptoms. Parents reported the child’s most recent school grades and the child’s typical sleeping and waking hours for school and after-school nights; they also answered a questionnaire about their child’s daytime sleepiness. After each visit, the children wore accelerometers on their right hips for one week, and the data was used as an objective measure of sleep onset and sleep duration each night.
The analysis was controlled for several potential confounding factors, including the child’s age at the start of the study, child’s gender and birth order, child’s and parents’ place of birth, parents’ marital status and educational level, family income, how often English was spoken at home and how far the child had progressed through puberty.
It doesn’t mean you can’t take the phone away from your child if you think they’re taking too long to fall asleep.
About 25% of children received phones at age 10.7 and 75% at age 12.6. Almost all children had phones by the age of 15. Among children who owned phones, 99% had smartphones by the end of the study. The timing of phone purchase by children was similar to that recorded in US cross-sectional samples.
The scientists investigated whether children’s well-being outcomes differed based on whether they had their own cell phones and what happened to their well-being outcomes when they acquired their own phones (the transition from not owning a phone to owning one). They also conducted analyzes to test whether children’s well-being differed depending on the age at which children received their first cell phone.
Initial comparisons of phone-owning status versus no-phone status showed some indication of differences: While the entire group’s depression scores declined over time, meaning they were less depressed, the decline was slower when children owned phones than when they did not. Possible effects on sleep were also noted: Parents reported that children got less sleep on school nights when they had a phone than when they didn’t — although this observation was not borne out by measures of children’s sleep from accelerometer data . . The accelerometer data showed that when the children did not have phones, they slept slightly more on nights outside of school.
There are no significant differences
However, when the team checked for the statistical effect of performing multiple comparisons on the same data set, none of these correlations met the criteria for statistical significance.
The researchers conducted further analyzes to see if children’s characteristics interacted with phone ownership in explaining their well-being outcomes. Cell phone ownership was associated with lower levels of depressive symptoms for boys than girls, and less depression for children with lower versus higher sexual maturity. Phone ownership was also associated with less sleep among children of higher maturity. These results highlight potential relationships to be examined more closely in future studies.
When analyzes were conducted on smartphones only (vs. all mobile phones), the results were similar.
The overall pattern of results indicates that, overall, technology mastery was found to be neither positively nor negatively related to children’s well-being. The researchers note that it may be more important to study what children are doing with their technology than simply whether they have a phone.
“These are population-level average trends,” Sun said. “There may still be individual differences. It doesn’t mean you can’t take the phone away from your child if you think they’re taking too long to sleep.”
The team is conducting research on how people use their phones as part of the Stanford School of Medicine’s ongoing Human Screenome Project.
Also, the scientists point out, the study did not give children completely unfettered access to phones, as their parents were making decisions about their technology use.
“At the level we can measure, time itself [of acquiring a phone] it doesn’t seem to be a key factor because it’s happening in the larger context of parenting,” Robinson said. “It’s not an argument for kids to tell their parents, ‘Look, there’s no influence of phones.’ Parents should use their best judgment as to what is right for their child, as they appear to be doing in fact.”
The research was supported by the National Heart, Lung, and Blood Institute (grant U01HL103629), the Stanford Data Science Fellowship, the Stanford Maternal and Child Health Research Institute, and the Stanford Department of Pediatrics.
The research team includes members of Stanford Bio-X, the Stanford Cardiovascular Institute, the Stanford Wu Tsai Human Performance Alliance, the Stanford Maternal and Child Health Research Institute, and the Stanford Cancer Institute, as well as collaborators from the Stanford Institute for Human – Focused Artificial Intelligence and the Stanford Woods Institute for the Environment.