Health experts nationwide are expressing increasing concern about the effects of time spent looking at phones, computers, tablets and TVs on the well-being of all Americans. A growing amount of data clearly suggests that, when it comes to screen time, less is more.
But most of us are spending more time in front of screens, not less. According to estimates from the CDC, Nielsen, Common Sense Media and others, children between the ages of 2 and 5 already are averaging around 32 hours per week of screen time. Between ages 8 and 10, kids spend an average of 6 hours a day looking at various screens; and by the time they reach 18, that average rises to more than 7.5 hours per day. Adults now average a whopping 11 hours every day looking at screen-based media, up from about 9.5 hours four years ago.
First and foremost, sitting or lying in front of a screen for hours every day keeps people sedentary, which has been shown in multiple studies to significantly raise the risk of cardiovascular disease, Type 2 diabetes, obesity and some cancers, including breast and prostate cancer. That risk increases with age, and seems to exist regardless of how often and how vigorously a person exercises, recent research also has shown.
The artificial blue light emitted by screens has been shown to contribute to a host of problems as well, especially at night. Many studies demonstrate that evening exposure to blue light disrupts the body’s natural sleep-wake cycle by inhibiting melatonin production in the brain, reducing both the quantity and quality of sleep. Estimates from the National Heart, Lung and Blood Institute [NHLBI] suggest that between 50 and 70 million Americans now have ongoing sleep disorders.
Blue light exposure may also alter naturally occurring levels of other hormones related to circadian rhythm, including the stress hormone cortisol, along with those of key neurotransmitters such as serotonin and dopamine – which has been connected in studies with increasing rates of obesity, anxiety and mood disorders among teens and adults.
As people of all ages spend more time staring at screens, there is also concern about potential harm to their visual health. According to the American Academy of Ophthalmology, there has been a marked increase in both children and adults with dry eye, blurred vision, and eye strain, along with an “epidemic” of nearsightedness and a rising risk of more serious long-term vision problems, including macular degeneration.
For kids, early exposure to screens on a daily basis means that negative health impacts may begin very early in life. For preschool-aged children in particular, whose brains are rapidly developing, screen time in excess of two hours per day may contribute to behavior problems including inattention and ADHD, according to recent research.
Evidence pointing to negative effects of excessive daily screen time on mental health – especially in adolescents, teens and young adults – is also plentiful. Screen-based interactions like social media and video games are increasingly taking the place of interacting in person. Although studies have drawn different conclusions about causality, rapid increases in rates of depression, anxiety disorders and suicidal thoughts among teens have frequently been linked to their screen habits.
One study published earlier this year found that just one in 20 American adolescents currently meets national recommendations for sleep, physical activity and screen time. That study’s author called the finding “a wake-up call for everyone who wants to make sure our children have a healthy future.”
So what can be done to mitigate these health risks? One obvious answer is to limit screen time as much as possible at early ages, and to keep it under the one hour per day recommended by pediatric health experts for kids younger than 5.
Enforcing limits may be more challenging with older children and teens, but research indicates it’s worth the effort: Setting a “screen curfew” of at least an hour before bedtime was recently shown to improve sleep, focus and mood in a large group of teenagers after just one week.
Similarly, adults who set limits on themselves by disengaging from their screens at night and allowing themselves to fall asleep naturally also can benefit from more restful sleep.