So mom was right after all: Too much television time can harm your brain.

A new study published in the Journal of the American Medical Association has found that watching television for extended periods – such as a day-long binge-watching session — can weaken your brain power over time.

The study, led by the University of California at San Francisco, tracked the TV and activity habits of more than 3,000 young adults for 25 years. At the end of the study, when participants had reached their 40s and 50s, they took three tests that assessed memory, concentration, and mental and physical agility.

The results would not surprise your mother: People who watched at least three hours of TV a day and got little activity performed worse on the cognitive tests compared with those who moved more and watched less TV.

The study raised questions about which came first: low cognition or excessive TV-watching. That is, those with low cognitive ability may be more inclined to sit and watch TV anyway. It also didn’t distinguish what types of TV shows people were watching, and whether it made a difference. Does watching the Science Channel instead of reality shows have the same effect? It’s also possible that watching more television means you’re not sufficiently challenging your brain. Addressing those questions requires more study, the researchers said.

But there’s no denying the age-old advice: everything in moderation. A little TV is okay, especially if you discuss it afterward with a friend or partner. Even talking with other people can keep your brain in the game, because conversations require mental effort. Switching up your daily routine, trying a new hobby and, of course, exercising can also give your brain a boost.