The medical community has known for the past 30 years that spending large amounts of time in front of a TV or computer screen had a negative effect on a child’s developing brain – but specifically what parts of brain development were affected and for how long, have not been well researched or understood.

Thanks to new longer-term research studies, we now have more comprehensive, useable data. The Journal of the American Medical Association recently reported in JAMA Pediatrics that an increase in screen viewing time is linked to poorer progress on key young childhood developmental measures over time, including communication and language skills, memory, attention span, problem solving, and social skills.

This pronouncement is the result of a far-reaching psychological study from the University of Calgary in Canada, where 2,441 mothers and children aged two to five were studied over the course of three years. Initial baseline data were collected at the start of the study, when the children were two years old, then again when they were three and five.

By following the children over many years, the University of Calgary study learned more about how screen time and early child brain development intersect. Mothers reported on how much time their children spent in front of a television or computer screen on a typical day. They also reported on their child’s developmental measures by answering questions about their child’s behavior, communication skills, and social interactions. The study found that on average, the young children in the study were spending about 2-3 hours per day in front of a screen. (It’s worth noting that The American Academy of Pediatrics recommends that young children spend no more than one hour a day watching quality educational programming.)

Children who spent more time using TV or computers did indeed show poorer performance on developmental measures. (Interestingly, the study did not find evidence that the opposite was occurring. In other words, children with developmental issues were not more likely to spend time in front of a screen.)

These measurable links remained strong even after researchers accounted for other factors that can influence development, such as parents’ education, children’s physical activity levels, and whether parents read to their children regularly.

“The study results show that there is a lasting influence of screen time, especially when children are two to five years old, when their brains are undergoing a period of tremendous development,” according to the JAMA Pediatrics article.

“It also strongly supports expert guidelines that recommend limiting screen time for young children,” notes Leanne O’Neil of INDY Neurofeedback. “When the brain is rapidly developing new connections, it learns from every kind of experience it receives. So when watching a screen, the child is missing out on the opportunity for interacting with others and the surrounding environment.”

It is important to note, however, that not all screen time is detrimental to brain development. Families can develop healthy media habits by watching with their children, pointing out and discussing interesting ideas to contribute to language, skills and learning, making the time beneficial.