Passing on the gym to snuggle on the couch and binge watch whole seasons of your favorite show this weekend may not bode well for your brain.

In a 25-year study that tracked more than 3,000 young adults into midlife, researchers found that those with the highest television watching and lowest physical activity scored worse on certain cognitive tests than their fit, less TV-addicted counterparts. In particular, couch potatoes had slightly lower brain processing speeds and worse executive function, but they scored just as well as other participants on verbal memory tests. The findings, reported in JAMA Psychiatry, may suggest that such bad TV and exercise habits early in life could set people up for faster cognitive decline in later life, the authors said.

However, the researchers can only speculate on cognitive decline for now, because they only tested cognitive skills at the end of the 25 years—not at the beginning. Therefore, it’s possible that participants with slightly lower cognitive function scores at the end of the study had those same low scores at the start and just enjoy spending lots of time lounging in front of glowing screens. Researchers can't tell from the data as is.

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