Why smartphones before age 12 raise risks of depression, obesity and poor sleep

Smartphones have become an everyday feature of modern life, not only for adults but also for children. Many parents use them to keep children calm, entertained, and connected, and often see them as a tool to help young people navigate peer pressure and social interactions. Yet, while parents frequently debate the right age for a child to own a smartphone, emerging research suggests that getting one too early may in fact be harmful.

A recent study published in the peer-reviewed journal Paediatrics, which analysed data from more than 10,588 young adolescents in the Adolescent Brain Cognitive Development (ABCD) Study, found that children who owned a smartphone by age 12 were significantly more likely to experience depression, poor sleep, and obesity in early adolescence than their peers who did not have a phone at that age.

At age 12, smartphone ownership was associated with a 31 per cent higher risk of depression, a 62 per cent increased risk of insufficient sleep, and a 40 per cent higher risk of obesity.

The earlier a child received their first smartphone, the greater the likelihood of these problems: with each year earlier a phone was acquired, the risks of obesity and sleep issues rose.

Poor sleep

Even among children who did not have a smartphone at age 12, receiving one within the next year was linked to a higher risk of mental-health challenges and poor sleep by age 13, compared with those who remained phone-free.

The researchers adjusted for factors such as demographics and socioeconomic status and still observed clear differences between children with and without smartphones.

By age 12, around 6.5 per cent of children with phones had been diagnosed with depression, compared with roughly 4.5 per cent of those without—a small but meaningful difference.

For obesity, about 18 per cent of smartphone users were classified as obese, compared with 12 per cent of children without phones.

Sleep was also notably affected: 47 per cent of 12-year-olds with phones reported getting fewer than nine hours of sleep per night, compared with 31 per cent of their peers without phones.

Among children who acquired a smartphone by age 13, the likelihood of mental-health issues, including depression and insufficient sleep, increased. However, the study found no significant change in obesity risk over that one year.

Wide range of risks

Early smartphone exposure has been linked to a wide range of risks beyond depression, poor sleep, and obesity.

Studies show that frequent smartphone use—especially on social media—can heighten anxiety and stress due to constant notifications, fear of missing out, and online social pressures.

Excessive screen time may also impair attention span, memory, and executive function, making it harder for children to concentrate on schoolwork or complete tasks without distraction. Behavioural issues such as irritability, impulsivity, and difficulties with self-regulation have also been associated with early smartphone use.

Other Topics To Read

• Headlines
• Health
• depression
• Smartphones
• Obesity
• children's health
• Kenya youth
• screen time
• adolescent mental health
• sleep deprivation
• social media use
• parenting guidance
• Why smartphones before age 12 raise risks of depression
• obesity and poor sleep

Children with early access to smartphones face greater exposure to cyberbullying, inappropriate content, online predators, and risky online behaviour. Increased screen time often replaces physical play, reinforcing sedentary habits, lowering fitness levels, and raising obesity risk.

Overreliance on digital interaction may also hinder social development, reducing face-to-face communication skills, empathy, and relationship-building.

Prolonged screen use can cause eye strain, headaches, and posture-related problems, including neck and back pain. In addition, blue-light exposure disrupts sleep quality and circadian rhythms.

Addictive tendencies

Some children may even develop addictive tendencies, including compulsive phone-checking and mood disturbances when separated from their devices.

While smartphones undoubtedly offer benefits for learning and connectivity, early and unsupervised use carries multiple physical, mental, and social risks. These require careful monitoring and guidance from parents and caregivers.

A survey by the Communications Authority of Kenya and the Kenya National Bureau of Statistics (KNBS) found that 53.7 per cent of Kenyans aged three and above own a mobile phone, whether a smartphone or another type of device.

Ownership is higher in urban areas at 64.6 per cent, compared with 48.6 per cent in rural areas. Among young adults aged 18–34, ownership is especially widespread, with over 80 per cent reported to own a mobile phone.

Globally, smartphone ownership among teenagers and young people is extremely high, with some sources placing the rate at above 98–99 per cent among internet users aged 16–20.

Global burden of disease

The World Health Organisation (WHO) estimates that around 1 in 7 adolescents (ages 10–19) experiences a mental-health disorder at any given time, including depression, anxiety, and behavioural problems. These conditions contribute significantly to the global burden of disease in young people.

In Kenya, recent regional research—particularly during and after the Covid-19 pandemic—has shown a high prevalence of depressive symptoms among adolescents. For instance, a study of adolescents in Nairobi and coastal areas found that 26 per cent reported depression and 19.1 per cent anxiety.

Another recent survey in coastal Kenya, the 2025 Mombasa Youth Study, reported that approximately 11.2 per cent of adolescents and young people exhibited symptoms of moderate to severe depression.