Karina Colombo, who will defend her doctoral thesis at the EUI on 19 May 2025, has been conducting research on child-rearing in two key stages of development – early childhood and adolescence – with a focus on the effects of screen use and exposure to high-speed internet on young children and adolescents. Her interest in these important phases of life dates back to her time as an undergraduate student.
“Both the positive and negative factors experienced during childhood have long-lasting effects, as children are a particularly vulnerable population that depends on adults for satisfying their needs,” comments Colombo.
After starting her PhD at the EUI Department of Economics, Colombo realised that the consequences of prolonged screen time in small children had not been sufficiently explored in academia. She therefore decided to focus the first part of her doctoral research on this subject and worked with Elisa Failache, who, at that time, was a PhD researcher at the Universitat Autònoma de Barcelona.
The research topic proved to be challenging from the start. “It is very hard to measure the effects of screen time on children given the difficulties in isolating the causal effects from other correlations,” explains Colombo. She clarifies this statement with an example that refers to television: “Is watching too much TV causing developmental delays in socioemotional skills of young children? Or are children who are behind in socioemotional skills more prone to watching TV?”
A second issue faced by the researchers was an ethical one. It would not have been correct to implement any experiment that would incentivise an increase in children’s screen time, since correlational evidence already indicated the possibility of harm. Therefore, Colombo and Failache had to find a different way to carry out their research.
The solution came from Colombo’s home country, Uruguay. She explains that Uruguay represents an interesting case study to analyse the effects of internet use given its remarkable growth in telecommunications, showing a digital development similar to European countries. Over the past decade, the government has implemented a wide array of policies to increase internet quality and to guarantee digital inclusion: a basic broadband plan that offered entry-level connectivity at no extra cost for households with landlines; the ‘one laptop per child’ programme; and the ‘Fiber to the Home’ (FTTH) project - which provided high-speed internet to all households with a fixed telephone line, free of charge. As a result, children and adolescents in Uruguay have access to fast internet and have substantially increased the time they spend online.
The researchers worked by combining data about the deployment of the FTTH project with data coming from a large survey on child development. What they found out was that an increase of 10% in lifetime exposure to fiber optics during early childhood decreases children’s development scores in communication, problem solving, and social skills. More precisely, in children ages zero to five, exposure to high-speed internet at home increases developmental delays in cognitive and non-cognitive skills. This is explained by an increase in children’s screen time and by a reduction in beneficial activities for child development, such as reading books.
“Since infants and toddlers learn at a very high pace, the use of screens has detrimental effects on them due to its high opportunity cost,” reveals Colombo, specifying that with ‘high opportunity cost’ she means the comparison of the few benefits of screen time with the much higher benefits of the activities that kids reduce to spend more time watching a screen. She says that this is often referred to in literature as the ‘video deficit’, meaning the lower ability for a young child to learn new skills from a video compared to live sources such as spending time with other children, adults, and with the surrounding environment.
Colombo explains that the World Health Organization (WHO) had issued guidelines that specify the maximum recommended time children should spend on screen-based sedentary activities. The WHO advises to avoid screens completely for children younger than 24 months and to limit sedentary screen time to no more than one hour for children from two to five. Moreover, the American Academy of Pediatrics provided some best practices during screen exposure for children. Colombo underlines that the outcomes of screen use on children are different according to the type of content consumed online (e.g. educational, fast-paced, violent, etc.), and the context in which the content is used (co-viewing with adults, before bed, while eating, to calm a tantrum, etc.).
Available data for different countries already indicated that caregivers do not comply with the medical recommendations on screen use for children, but Colombo and Failache wanted to prove it. They performed a field experiment to answer these questions: Are parents not aware of these recommendations? Or are they aware, but it is too costly in terms of effort to follow them?
The researchers did an experiment with caregivers of children aged zero to five. They put together a sample of 2,341 caregivers and split it into a treatment group and a control group. They provided the treatment group with an online video and a digital leaflet that summarised the WHO’s main recommendations on screen use. They also created an extensive survey that allowed them to analyse the level of compliance with the screen exposure recommendations. The survey measured the screen quantity time throughout the week, including both primary exposure and secondary one (meaning while doing other activities). It also focused on the quality of screen exposure and evaluated six dimensions regarding parent-child practices during screen use: co-viewing with adults, content quality, use of parental control, moments of exposure, rules for screen exposure, and background exposure.
“The results of this experiment show that the level of compliance of caregivers with the medical recommendations on screen use in children given by international health institutions is low,” reveals Colombo, underlying that more than three-quarters of the children do not comply with the screen time limit suggested by the WHO. Moreover, almost 60% of children watch mostly non-educational videos, around half of them are exposed to content that is not suitable for their age, 18% of children use screens during meals, and almost one-fifth before bedtime. Finally, 29% of caregivers never use parental control, and almost 60% of parents use screens to calm their children.
“There is clearly significant room for improvement in the fulfillment of screen exposure recommendations,” comments Colombo, adding, however, that most caregivers were familiar with some of the recommendations. Moreover, 65% of caregivers claimed it would be arduous for them to reduce their children’s screen time, and around 68% of parents not co-viewing content with their children stated that it would be too tiring for them to do so.
The second part of Colombo’s doctoral research, co-authored with Elisa Failache and Martina Querejeta, former PhD researcher at Universidad de la República in Uruguay, shifts the focus from childhood to adolescence. The researchers analysed the causal effect of exposure to high-speed internet on the socioemotional wellbeing in adolescence, which represents a particularly vulnerable stage for mental development.
For this part of the work, they used a dataset they had built for a previous project and combined it with a large survey on adolescence which included validated questions on self-reported symptoms of poor mental health in adolescents. Colombo explains that the results of this research go beyond a particular sub-population of adolescents and can be widely applied to all youth living in urban areas.
This research, published on the Journal of Population Economics, proves that high-speed-internet has mixed effects on adolescents and youth.
Colombo reveals that going from zero to a 100% probability of an in-home internet connection decreases the probability of adolescents feeling lonely by 9%. However, it also increases the probability of adolescents feeling worried by the exact same percentage. She specifies that, while the effect on feeling worried is widespread, the reduction in loneliness is mostly felt among boys and individuals with lower educational background. Finally, she mentions an increase in the probability of having a medical visit of 11% for adolescents highly exposed to the internet, without statistically significant effects in visits to a psychologist or psychiatrist.
“These findings illustrate the complexities of internet accessibility, where the use of new technologies results in both benefits and risks for adolescents that also depend on background characteristics,” comments the EUI researcher, stressing that “for adolescents and youth, the results of our research are not so black and white.”
As Uruguay is pretty similar to European countries, when it comes to the accessibility of fast speed internet, Colombo underlines that her research findings can inform policy design for children and adolescents in Western countries. The EUI researcher hopes that her work will contribute to support caregivers and young people by providing them with the adequate tools to minimise risks from internet exposure while taking advantage of its benefits.
“Young people use the internet as a way of being connected with others, but this may also entail negative consequences in other aspects of life. Our results highlight the benefits and risks of new types of social interactions that emerged with the rise of high-speed internet,” Colombo concluded. “The internet has affected countless aspects of our lives, posing benefits and risks to young people’s wellbeing, and understanding the potential effects of these new technologies is essential.”
Karina Colombo is a researcher at the EUI Department of Economics. Her thesis title is ‘Economics of Parenting: Evidence from Early Childhood and Adolescence’. Karina’s thesis supervisor is former EUI Professor Sule Alan, while her co-supervisor is former EUI Professor Thomas Crossley.
Read the paper ‘High-speed internet and socioemotional wellbeing in adolescence and youth’ by Karina Colombo, Elisa Failache, and Martina Querejeta, published on the Journal of Population Economics.
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