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Why Limit Screen Time? Scientific Research Explains

November 18, 2010 by Sherrelle Walker, M.A

limit screen time

This past September in a blog posting about the importance of physical exercise, I opened with a comment about the powerful pull that the video screen exerts on young brains. To be sure, this useful evolutionary adaptation has served us very well. Our instinctive ability to focus and concentrate on fast-moving, bright stimuli is a survival mechanism that allowed our ancestors to escape from many a tight spot. Even so, with the advent of modern technologies such as computers and television, we are now experiencing the down side of an endless flood of engaging electronic input. Research has shown that extensive screen time has the power to negatively affect our very chemistry and biology.

As we know from brain plasticity research, the stimuli we receive over time directly affect the development and wiring of the brain. Still, these effects are only the beginning of a long list of problems that screen time engenders. This past September, British psychologist and biologist Aric Sigman published an article in the British MailOnline that pulls together the conclusions of recent research from around the globe, painting a clear picture of the deleterious effects of screen time, and that picture is far from pretty. In fact, it is one that we, as parents, as teachers and as members of a national community, must not ignore.

While screen time has been shown to have negative psychological effects, I found Sigman's run-down of the chemical and biological effects to be of particular concern:

Suppression of melatonin release: Healthy levels of melatonin help regulate sleep, the immune system, and the onset of puberty. When children who watched an average amount of TV had all screen time removed, their melatonin levels went up by 30 percent after one week.
Increased chance of coronary heart disease: A study of 290 boys aged 15 showed that those who averaged over two hours of screen time a day had "elevated levels of chemical markers related to the development of coronary heart disease in later life." A different study out of Melbourne showed that for each hour an adult watches TV a day, there is an 18 percent increase in the likelihood that this adult will die from heart disease. Says Sigman, "Those who watched four or more hours were 80 percent more likely to suffer a fatal heart condition."
Changes in chemicals related to hunger and feeling satisfied: After 45 minutes of screen time, subjects consumed 230 calories more than those who had no screen time. Also, women who watched TV during a meal were more likely to snack later on.
Elevated blood cholesterol: Individuals between five and 15 who watched more than two hours a day were more likely to have raised blood cholesterol later in life.
Release of dopamine: Screen time causes the release of dopamine, a chemical that contributes to learning and concentration. As a result, our brains may become desensitized to the effects of normal levels of dopamine, making it hard to concentrate and focus on non-screen-based stimuli.

Taken in sum, these studies are sending us a clear message that we as parents and educators must take to heart: the more these screen-based technologies occupy time in our days, the more vigilant we must be about maintaining our own healthy habits, as well as educating our students to the risks so they can make their own smart decisions and lead long, healthy lives.

Learn more about the effects of screen time: