The fact that too much TV can result in attention problems is well known but least supported by data. To delve deep into the issue Landhuis and his colleagues investigated 1,037 girls and boys born in 1972 and 1973, tracking them from age 5 to 15.

Normally kids were watching 3.13 hours of TV on an average weekday when they are in the age 13 to 15 and about 2 hours of TV daily when they were 5 to 11 years old.

Study participants who had watched more than 2 hours of TV in early childhood were more likely to have attention problems as young teens, the researchers found. Those who watched more than 3 hours were at even greater risk.