Sitting in front of the TV for hours on end really does impair your mental ability, according to a new study in the journal JAMA Psychiatry.
By studying the link between TV-watching and cognitive functioning in Americans, researchers from the Universities of California and San Francisco found that on average, the more TV people watched, the worse they performed in a series of intelligence tests.
Their study extended over a 25-year period, looking at over 3,000 adults aged between 18 and 30 who were put into categories according to how much TV they watched on average.
Mental ability was determined by assessing processing speed and verbal functioning, and overall the researchers found big TV fans were twice as likely to have poor mental functioning by the end of the test.
Also from the study, but slightly less surprising, was the fact low physical activity has a negative impact on the mind.
"We found that low levels of physical activity and high levels of television viewing during young to mid-adulthood were associated with worse cognitive performance in midlife,” the researchers wrote.
In particular, these behaviours were associated with slower processing speed and worse executive function but not with verbal memory.
Participants with the least active patterns of behaviour (i.e., both low physical activity and high television viewing time) were the most likely to have poor cognitive function.. Individuals with both low physical activity and high sedentary behaviour may represent a critical target group.