Netflix and chill doesn’t do you any favors. (Stocksy)
You’ve heard the mantra before: “TV rots your brain.” But new research has found it might actually be legitimate.
According to a study published in the journal JAMA Psychiatry, binge-watching TV in your 20s is linked to cognitive decline 25 years down the road.
For the sweeping study, researchers asked 3,257 people between the age of 18 and 30 to answer questions about their TV and exercise habits during regular check-ins over 25 years. At the end of the 25 years, scientists evaluated participants’ cognitive function via tests that measured processing speed, executive function, and verbal memory.
Here’s what they found:
10 percent of people watched three or more hours of TV each day (for at least two-thirds of the check-ins). They were significantly more likely to do poorly on the tests.
People who did the least amount of physical activity (less than 2.5 hours a week) also performed poorly on some of the tests.
People who showed the most cognitive decline were heavy TV viewers that didn’t exercise much or at all — they were more than twice as likely to perform badly on the tests.
That’s startling news, given that the average American watched five hours of TV a day in 2014, according to Nielsen data.
Related: Is Your TV Trying To Kill You?
But TV’s link to negative health effects is nothing new. A University of Pittsburgh study published in April found that each hour of TV we watch daily increases our risk of developing diabetes by 3.4 percent.
Another study published in the British Journal of Sports Medicine discovered that every hour of TV we watch shortens our life expectancy by 22 minutes. And watching two hours of TV or more a day is linked to an increase risk of heart disease and early death, per a 2011 Harvard study.
Excessive TV-watching is also linked with depression. Research from the University of Texas at Austin published earlier this year found that the more depressed and lonely a person is, the more likely they are to binge-watch TV.
Researchers say the latest study is one of the first to demonstrate a link between TV viewing time, exercise, and cognitive decline.
“Our study suggests that … that we need to start thinking more about how our screen behaviors might affect cognitive function,” lead study author Tina Hoang, MSPH, tells Yahoo Health.
It’s worth noting that Hoang and her co-authors, including Kristine Yaffe, PhD, a professor at the University of California, San Francisco, School of Medicine, found that people who watched a lot of TV but had high levels of physical activity weren’t more likely to have poor cognitive performance.
Hoang says the link might be explained by a couple of factors. One is that TV watching may cluster with other behavioral patterns, like eating a poor diet, which can impact your cognitive ability over time. She also points out that most people are more sedentary when they watch TV instead of being physically active, which can raise their cardiovascular risk factors (and eventually impact their cognitive ability).
But Clifford Segil, DO, a neurologist at California’s Providence Saint John’s Health Center tells Yahoo Health that he’s not sure TV is all that bad for our brains.
He acknowledges that people who watch a lot of TV and don’t exercise often aren’t as coordinated motor skill-wise, but he points out that there are a lot of smart people that watch a lot of TV. “It makes sense that you might not be an intense jock if you watch a lot of TV, but you might be a smart nerd,” he says.
Segil says TV can actually be good for your brain in moderation because it can act as a de-stressor, provides visual and auditory simulation, and forces you to focus.
But not all TV is created equal. Binge-watching soap operas during the day isn’t going to do as much for your brain power as following a National Geographic special, sports game, or even Game of Thrones. “Shows that have plot twists make you focus and engage you mentally,” Segil says. “That stimulates conversation with friends, which can also be beneficial.”
Researchers acknowledge in the latest study that watching a lot of TV doesn’t necessarily cause cognitive decline later in life — just that there’s a link. While it’s possible that watching too much TV and not getting enough exercise can cause health issues that may impact your brain function, it’s also possible that people with low cognitive function are simply more likely to watch more TV.
What we do know: Watching some TV is OK, but if you’re not doing your health (or your social life) any favors if you regularly park on the couch and binge-watch TV for hours at a time.